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Overview and Recommendations
Background
- •Community-acquired pneumonia (CAP) is defined as an acute infection of the lung parenchyma acquired outside a hospital or long-term care facility, confirmed by a new pulmonary infiltrate on imaging and compatible clinical features. It is the leading infectious cause of hospitalization among U.S. adults, with an annual incidence of 24.8 per 10,000, rising to 164.3 per 10,000 in those aged ≥80 years.
- •The etiologic spectrum is dominated by Streptococcus pneumoniae (the most common bacterial cause), followed by Haemophilus influenzae, Mycoplasma pneumoniae, Legionella species, respiratory viruses (influenza, SARS-CoV-2, rhinovirus), and, in immunocompromised hosts, Pneumocystis jirovecii and fungi. Atypical pathogens (Mycoplasma, Chlamydophila, Legionella) account for 20-30% of cases and require distinct antibiotic coverage.
- •Key risk factors include smoking (OR 2-4), COPD, diabetes, chronic heart disease, alcoholism, poor dental hygiene, and aspiration risk (dysphagia, neurologic disease). HIV remains a dominant driver in sub-Saharan Africa (seroprevalence ~78% in hospitalized CAP). Smoking cessation and pneumococcal/influenza vaccination are the most impactful modifiable preventive measures, with pneumococcal vaccine reducing CAP in COPD patients (NNT = 21).
- •CAP is classified by etiology (typical vs. atypical), severity (outpatient, ward, ICU), host immune status, and aspiration risk. Aspiration CAP accounts for 25% of cases in older adults and independently doubles mortality. The historic category 'healthcare-associated pneumonia' (HCAP) has been abandoned due to lack of outcome benefit from broad-spectrum therapy; current guidelines favor individual risk assessment for multidrug-resistant pathogens.
- •The pathophysiology involves microbial invasion overcoming alveolar macrophage defenses, triggering innate immune activation, alveolar-capillary barrier disruption (driven by microenvironmental acidification to pH ~6), and systemic inflammation. Transcriptomic profiling identifies two sepsis response signatures: SRS1 (immunosuppressed phenotype, 41% of patients) with 14-day mortality HR 2.4, and SRS2 (inflamed). This host-response heterogeneity explains why mortality has remained static despite antibiotics.
- •Long-term outcomes are poor: over 9.8 years of follow-up, CAP survivors have an adjusted HR for death of 1.65, with 30-day readmission rate of 15.7%. Cardiovascular complications (myocardial infarction, new atrial fibrillation, heart failure) affect 18-30% of hospitalized patients and drive in-hospital and post-discharge mortality. Pneumolysin and hydrogen peroxide from S. pneumoniae directly invade myocardium, causing necroptosis and scarring.
Evaluation
- •Suspect CAP in any patient with acute cough, fever, dyspnea, pleuritic chest pain, or unexplained fatigue, symptoms typically evolve over 1-7 days. In elderly patients, fever and cough are often absent; instead, look for confusion, falls, functional decline, or anorexia. Auscultate for crackles, bronchial breath sounds, egophony, and dullness to percussion (LR+ 2-6 for bronchial breath sounds). Tachypnea >30/min, hypotension, or hypoxemia (SpO₂ <90%) signal severe disease.
- •Confirm the diagnosis with a chest radiograph showing a new infiltrate (lobar, multilobar, or interstitial). Up to 33% of infiltrates are missed on plain film; if clinical suspicion remains high despite a negative radiograph, obtain a chest CT or lung ultrasound. CT modifies management in 59% of cases, initiating antibiotics in 16% and discontinuing in 9%.
- •Assess severity immediately to determine site of care. Use CURB-65 (Confusion, Urea >7 mmol/L, Respiratory rate ≥30, Blood pressure <90/60, age ≥65), a score ≥2 recommends admission, ≥3 suggests ICU. The Pneumonia Severity Index (PSI) has higher sensitivity (NPV 0.98 for mortality) and is better for identifying low-risk outpatients. For ICU triage, the IDSA/ATS 2007 minor criteria (≥3 of 9) have sensitivity 94% for need for mechanical ventilation or vasopressors.
- •Order bilateral blood cultures only in severe CAP (ICU admission or septic shock), positivity rate ~10%. Obtain sputum Gram stain and culture if a purulent specimen can be collected. For all hospitalized patients, perform pneumococcal urinary antigen (sensitivity 60-75%, specificity 99.7%) and Legionella urinary antigen (serogroup 1, sensitivity ~70%). Add a respiratory viral PCR panel (nasopharyngeal swab) to identify influenza, SARS-CoV-2, RSV, and other viruses.
- •Check laboratory markers: CRP and procalcitonin (PCT) are complementary. In early presenters (<3 days of symptoms), CRP may be low and PCT high ; in later presenters, CRP rises and PCT falls. A PCT <0.25 ng/mL can help defer antibiotics in low-risk outpatients. Also obtain renal function (creatinine, urea), liver enzymes, and CBC. For hypoxemic patients, an arterial blood gas defines PaO₂/FiO₂ ratio (<300 indicates respiratory failure) and PaCO₂.
- •Consider additional testing in special populations: in immunocompromised hosts (HIV, transplant, neutropenia), broaden workup to include BAL with metagenomic NGS for Pneumocystis, CMV, fungi, and mycobacteria. In patients with aspiration risk factors (dysphagia, bedridden, enteral feeding), assess with volume-viscosity swallow test. For patients from endemic areas, add serology for Coccidioides or Histoplasma.
- •Evaluate for complications early: if a patient fails to stabilize by 48-72 hours, repeat blood cultures, obtain a chest CT, and consider bronchoscopy with BAL for culture and targeted NGS. Look for parapneumonic effusion (5-12% of CAP), empyema, lung abscess, or noninfectious mimics like vasculitis, organizing pneumonia, or pulmonary embolism.
- •Consider alternative diagnoses in non-responders: pulmonary embolism (especially if D-dimer >3.13 mg/L in elderly), heart failure, malignancy causing post-obstructive pneumonia, drug-induced pneumonitis, or granulomatous disease (TB, fungal). In patients with prior antibiotic use, structural lung disease (COPD, bronchiectasis), or chronic steroid use, consider Pseudomonas aeruginosa or MRSA, use the PES score to risk-stratify for these drug-resistant pathogens (NPV 98% at score <5).
- •Document clinical stability criteria daily: temperature ≤37.2°C, heart rate ≤100/min, respiratory rate ≤24/min, systolic BP ≥90 mm Hg, SpO₂ ≥90% on room air. Once stable for 48-72 hours, plan IV-to-oral switch and discharge. Procalcitonin guidance can shorten antibiotic duration: use PCT <0.1 µg/L to strongly discourage antibiotics, <0.25 µg/L to discourage, this reduces exposure by 48% without worsening outcomes.
Management
- •Start empiric antibiotics immediately after diagnosis, within 4 hours of presentation. For outpatients (CURB-65 0-1, PSI I-II): prescribe oral 1 g three times daily OR 200 mg loading then 100 mg twice daily for 5 days (minimum 3 days if clinically stable). Alternatively, 500 mg orally on day 1 then 250 mg days 2-5 can be used if local macrolide resistance rates are low.
- •For non-ICU hospitalized patients (CURB-65 2-3): initiate a beta-lactam plus a macrolide. Preferred: 2 g IV daily PLUS 500 mg IV daily. Alternatives: 1 g IV q8h, 1.5 g IV q6h, or 750 mg IV daily as monotherapy. Beta-lactam monotherapy is acceptable in patients without SIRS or ≥2, based on CAP-START trial noninferiority.
- •For ICU patients (severe CAP, CURB-65 ≥4, IDSA/ATS major criteria): initiate 2 g IV daily plus 500 mg IV daily OR 750 mg IV daily. The network meta-analysis identifies ceftriaxone plus levofloxacin as having highest probability for mortality benefit. For patients with risk factors for Pseudomonas (COPD, bronchiectasis, prior antibiotics, corticosteroids), use 4.5 g IV q6h or 2 g IV q8h plus an antipseudomonal fluoroquinolone (ciprofloxacin or levofloxacin).
- •In suspected MRSA (cavitary infiltrates, prior MRSA, IV drug use, end-stage renal disease), add 15-20 mg/kg IV q12h (target trough 15-20 µg/mL) or 600 mg IV q12h. Do not routinely cover MRSA or Pseudomonas in low-risk patients; the PES score (≥5: high risk) helps discriminate.
- •For severe CAP requiring ICU care, add adjunctive hydrocortisone 200 mg IV daily (continuous infusion or divided q6h) for 4-7 days, then taper. The CAPE COD trial demonstrated reduction in 28-day mortality from 11.9% to 6.2% (NNT = 18). The benefit is concentrated in patients with CRP >204 mg/L (OR 0.43 for mortality). Do NOT use corticosteroids in nonsevere CAP, prednisolone 40 mg daily increased late failure (19.2% vs 6.4%).
- •Provide oxygen to target SpO₂ ≥92% (PaO₂ ≥60 mm Hg). For moderate hypoxemic respiratory failure (PaO₂/FiO₂ 210-285), use helmet CPAP, median time to PaO₂/FiO₂ >315 is 1.5 h vs 48 h with standard oxygen. If CPAP fails or PaO₂/FiO₂ <150, escalate to noninvasive ventilation (NIV) or high-flow nasal oxygen. NIV reduces intubation risk (OR 0.26) and ICU mortality (OR 0.28) in CAP with ARDS.
- •For invasive mechanical ventilation, use lung-protective strategy: tidal volume 6 mL/kg predicted body weight, plateau pressure ≤30 cm H₂O. In severe ARDS, consider prone positioning and early neuromuscular blockade. In extreme cases, ECMO may be considered in specialist centers.
- •Monitor for clinical stability daily. Once stable for 48-72 h, switch from IV to oral antibiotics. Use procalcitonin guidance to limit duration: for nonsevere CAP, treat for 5 days (minimum 3) if stable; for severe CAP, treat for 5-7 days. Longer courses reserved for complications (empyema, lung abscess, necrotizing pneumonia). Do NOT extend beyond 7 days routinely, inflection point at 7.4 days associates with increased length of stay.
- •If no response by 72 h, evaluate for complications: repeat chest CT, bronchoscopy with BAL for culture and metagenomic NGS. Consider pleural drainage for parapneumonic effusion (chest tube with fibrinolytics: urokinase or alteplase). For empyema, VATS is preferred if fibrinolytics fail. Drainage of complicated effusion reduces hospital stay by ~5 days.
- •For patients with aspiration pneumonia (gravity-dependent opacity, dysphagia risk): cover anaerobes with 3 g IV q6h, , or 500 mg IV q8h added to a beta-lactam. Avoid clindamycin due to high resistance rates.
- •What NOT to do: Avoid NSAIDs in early CAP, they increase odds of pleuropulmonary complications (empyema, cavitation) 8-fold. Do not use benzodiazepines routinely, they increase CAP incidence (OR 1.54) and mortality (HR 1.22). Do not use corticosteroids for parapneumonic effusions (no benefit, trend toward harm). Do not use routine antifungal coverage in immunocompetent patients.
- •When to refer: Consider infectious disease consultation for immunocompromised hosts, patients with drug-resistant pathogens, or refractory cases. Consider pulmonary consultation for bronchoscopy, chest tube drainage, or advanced ventilatory support. For patients with functional decline after hospitalization, refer to pulmonary rehabilitation.
- •Discharge planning: Ensure all patients receive pneumococcal vaccination (PCV13 or PCV20 + PPSV23 per schedule) and influenza vaccination (in season). Assess cardiovascular risk: check high-sensitivity troponin and consider optimizing guideline-directed medical therapy for heart disease. Screen for dysphagia in elderly. Educate on smoking cessation and dental hygiene.
- •Antibiotic drug doses in special populations: Renal impairment, adjust beta-lactams, fluoroquinolones, vancomycin based on eGFR. Obesity, use actual body weight for aminoglycosides, adjusted body weight for vancomycin. Elderly, no specific dose changes for most beta-lactams and macrolides, but monitor renal function. Pregnancy, beta-lactams and azithromycin are safe; avoid tetracyclines and fluoroquinolones.
Board Review — High Yield
- •CURB-65, Clinical score for severity: Confusion, Urea >7, RR ≥30, BP <90/60, age ≥65; ≥2 recommends admission, ≥3 suggests ICU.
- •Procalcitonin (PCT), Biomarker to guide antibiotic initiation and duration; <0.25 ng/mL discourages antibiotics in low-risk outpatients; <0.1 µg/L strongly discourages.
- •CAPE COD trial, Demonstrated hydrocortisone 200 mg IV daily reduces 28-day mortality in severe CAP from 11.9% to 6.2% (NNT=18); benefit concentrated with CRP >204 mg/L.
- •PES score, Predicts drug-resistant etiology (Pseudomonas, ESBL, MRSA); score ≥5 had NPV 98% for ruling out non-core pathogens.
- •Long-term mortality, CAP carries HR 1.65 for death over 9.8 years vs controls; 30-day readmission rate 15.7%; need vaccination and CV risk modification after discharge.
- •Aspiration CAP, Independent predictor of mortality (HR 5.69); screen for dysphagia; cover anaerobes with ampicillin-sulbactam or metronidazole-beta-lactam combination.
- •SRS1 transcriptomic signature, Immunosuppressed phenotype in 41% of CAP patients; associated with higher 14-day mortality (HR 2.4); identifies candidates for immunomodulation.
- •Urinary antigen testing, Pneumococcal (sensitivity 60-75%, specificity 99.7%) and Legionella (serogroup 1) are rapid, noninvasive tests that increase diagnostic yield in hospitalized CAP.
- •Helmet CPAP, In moderate hypoxemic respiratory failure (PaO2/FiO2 210-285), improves oxygenation faster than standard oxygen (1.5 h vs 48 h to reach PaO2/FiO2 >315).
- •Pneumococcal vaccination NNT, In COPD, 21 patients need to be vaccinated to prevent one episode of CAP (OR 0.62). Influenza vaccine reduces symptomatic influenza by 70%.
Deep Dive — Evidence Details
1. Definition, Classification and Nomenclature
- ▸CAP is a clinical syndrome classified by acquisition setting, care location, severity, host response, and suspected or confirmed aetiology. [1,35]
- ▸Hospitalized CAP, ICU CAP, and severe CAP are overlapping but non-equivalent categories; ICU-based and ATS-based severe CAP definitions identify different populations. [428]
- ▸Aspiration-associated CAP, viral or pathogen-specific pneumonia, mixed infection, necrotizing pneumonia, and pediatric PARDS-associated phenotypes should be named when clinically supported. [34,35,425,426,431,432,435]
- ▸Machine-learning, metagenomic, and biomarker-defined phenotypes are emerging classification frameworks and are not yet universal diagnostic nomenclature. [5,40,425,432]
Definition
Community-acquired pneumonia (CAP) is best understood as an acute pneumonia syndrome acquired outside the hospital setting or not otherwise classified as healthcare-associated, with classification based on the clinical context, severity, host response, and suspected or demonstrated aetiology. The 2026 American Thoracic Society (ATS) guideline addresses diagnosis and management of CAP in adults and reflects contemporary recognition that diagnostic methods, including lung ultrasound, and treatment strategies continue to evolve. [1]A1c The 2025 French multidisciplinary guideline similarly defines its scope as CAP of presumed bacterial origin requiring outpatient, hospital, or critical-care management. [35]A1c
CAP is a syndromic diagnosis rather than a purely microbiological label. Pathogen-based classification may be limited because a causative organism is not always identified, while clinical metagenomics and other emerging technologies may reveal biologically meaningful heterogeneity beyond conventional culture-based categories. [1]A1c[40]B3b Host-response and inflammatory phenotypes can also distinguish clinically important subgroups, particularly in severe disease and in children. [5]B2b[40]B3b[425][432]
Core classification
CAP should first be classified by site and context of acquisition: outpatient CAP, hospitalized non-ICU CAP, and severe or ICU-level CAP. The French guideline explicitly frames CAP management across these three care settings. [35]A1c Hospital admission alone is not synonymous with severe CAP. In contemporary US data, severe community-acquired bacterial pneumonia (sCABP) has been operationalized either by ICU admission or by ATS major criteria, and these definitions identify overlapping but non-identical populations. [428]
Severity classification is clinically consequential. In the US study, 24.5% of CAP bacterial admissions met at least one sCABP definition; 51.2% met the ICU-based definition, whereas 78.0% met the ATS-based definition. [428] These findings demonstrate that “severe CAP,” “ICU CAP,” and “CAP requiring hospitalization” should not be used interchangeably. [428] Severity may also be estimated with established bedside scores such as CURB-65, although inflammatory indices—including neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios—have been investigated as adjunctive markers rather than replacements for validated clinical assessment. [429][436]
Aetiological and clinical subtypes
CAP may be described as bacterial, viral, atypical, fungal, mixed, or pathogen-unknown according to available microbiological and clinical evidence. The 2025 French recommendations specifically address presumed bacterial CAP, whereas contemporary evidence emphasizes that CAP can arise from diverse pathogens and that mixed infections are clinically relevant, particularly in pediatric cohorts. [35]A1c[40]B3b[432] Mycoplasma pneumoniae is a recognized CAP pathogen and may be associated with extrapulmonary disease, including Mycoplasma pneumoniae-induced rash and mucositis (MIRM); therefore, CAP nomenclature should not imply that disease is confined to the lungs. [222]B2a
Viral pneumonia may be included within the broader CAP syndrome, but pathogen-specific entities should be named when established. CAP and COVID-19 pneumonia can show similar circulating cytokine profiles while involving divergent biological pathways, supporting separate pathogen-specific nomenclature when SARS-CoV-2 is confirmed. [435]C Influenza-associated pneumonia is another distinct etiological subtype; critically ill patients with influenza may develop influenza-associated pulmonary aspergillosis (IAPA), even without classical risk factors. [426]
Aspiration-associated CAP should be identified separately when aspiration is clinically implicated. Aspiration community-acquired pneumonia (ACAP) is common among older adults and has been associated with worse outcomes than nonaspiration CAP, including differences in hospital stay, ICU admission, and mortality. [34]B2a However, aspiration-induced lung injury after acute drug or ethanol poisoning is a related but not automatically synonymous diagnosis; in that setting, impaired airway reflexes and aspiration may produce lung injury that requires separate consideration from infectious CAP. [429]
Complicated and phenotype-based nomenclature
CAP may be further qualified by complications such as necrotizing pneumonia, respiratory failure, acute respiratory distress syndrome, or cardiovascular complications. Adult necrotizing pneumonia is an uncommon complication of CAP with substantial morbidity, prolonged hospitalization, and uncertain consensus regarding radiological criteria and antibiotic duration. [431] In children, inflammatory biomarker patterns at admission have been studied for associations with severe CAP and pediatric acute respiratory distress syndrome (PARDS), indicating that pediatric severity phenotypes should not simply be extrapolated from adult classifications. [425]
Modern classification increasingly incorporates host-response biology. Machine-learning models have been developed to quantify immune dysregulation across pneumonia and sepsis populations, potentially separating clinical severity from the underlying biological response. [5]B2b In severe CAP, metagenomic profiles have been used to identify microbiome-based subtypes, while pediatric models have integrated microbiology, inflammatory markers, and clinical features to identify mixed-infection phenotypes. [40]B3b[432] These approaches remain phenotyping and research frameworks rather than universally accepted nomenclature. [40]B3b[432]
Finally, CAP classification should recognize outcomes extending beyond the acute episode. Long-term mortality after hospitalization has prompted development of the 1-year Long-term Pneumonia Mortality Index, and hospitalization for CAP has been associated with subsequent noncommunicable disease risk and cardiovascular events in observational studies. [12]B2b[430][434] These findings support documenting CAP as an index event with potential long-term consequences, while avoiding the unsupported assumption that every later event is directly caused by pneumonia. [12]B2b[430][434]
| Classification axis | Useful terminology | Evidence-based qualifier |
|---|---|---|
| Care setting | Outpatient, hospitalized non-ICU, severe/ICU CAP | Care setting is central to guideline scope, but hospitalization alone does not define severe CAP. [35]A1c[428] |
| Severity | Severe CAP, ICU CAP, sCABP | ICU admission and ATS major-criteria definitions are not identical. [428] |
| Aetiology | Bacterial, viral, atypical, fungal, mixed, pathogen-unknown | Mixed infection and pathogen-specific entities are increasingly recognized. [35]A1c[40]B3b[426][432][435]C |
| Aspiration | Aspiration-associated CAP (ACAP) | Should be distinguished from noninfectious aspiration-induced lung injury when appropriate. [34]B2a[429] |
| Complication | Necrotizing pneumonia, PARDS-associated CAP | These terms describe complications or phenotype-linked severity, not separate acquisition settings. [425][431] |
| Biological phenotype | Immune-dysregulated, metagenomic, inflammatory, mixed-infection phenotype | Primarily emerging or research classifications. [5]B2b[40]B3b[425][432] |
2. Pathophysiology and Mechanism
- ▸CAP pathophysiology combines pulmonary infection, restrictive dysfunction, ventilation–perfusion imbalance, systemic inflammation, oxidative stress, metabolic disturbance, and host susceptibility. [70,435,442]
- ▸SpO2/FiO2, PTX3, and mid-regional pro-adrenomedullin are among the investigated predictors of clinical failure. [437]
- ▸In adults aged ≥65 years, stress hyperglycaemia is associated with delirium, with only limited mediation by NLR and PCT. [438]
- ▸Gut dysbiosis and depletion of short-chain-fatty-acid-producing organisms support, but do not prove, a gut–lung-axis mechanism. [441,443]
- ▸Bacterial–viral co-infection, S. anginosus group infection, immunosenescence, and changing M. pneumoniae resistance patterns contribute to mechanistic heterogeneity. [439,444,447]
Overview
Community-acquired pneumonia (CAP) is a heterogeneous infectious syndrome in which pathogen characteristics, host immunity, pulmonary injury, and systemic metabolic responses jointly determine clinical severity and outcome. Contemporary studies show that CAP cannot be explained by a single inflammatory pathway: biologically distinct responses may occur despite broadly similar circulating cytokine profiles, and clinical deterioration may reflect interactions among pulmonary gas-exchange failure, dysregulated inflammation, oxidative stress, metabolic disturbance, and organ dysfunction. [435]C
Pulmonary infection and gas-exchange failure
Infection and inflammation within the distal airways and alveoli can produce restrictive pulmonary dysfunction and ventilation–perfusion imbalance, mechanisms associated with impaired oxygenation in CAP. [70]A1b The oxygen saturation-to-inspired oxygen fraction ratio (SpO2/FiO2) was among the individual parameters associated with outcome prediction in a prospective cohort, supporting the importance of oxygen-transfer impairment as a marker of disease severity. [437] In children hospitalised with CAP, greater cumulative intravenous-fluid exposure during the first 24 hours was investigated as a potential contributor to later respiratory deterioration, because excess fluid may increase pulmonary interstitial or alveolar water in inflamed lungs and worsen gas exchange. [445]
Severe pulmonary inflammation may progress to acute respiratory distress syndrome (ARDS), in which inflammatory and fibroproliferative pathways contribute to alveolar–capillary injury and respiratory failure. [446]D Corticosteroid effects in ARDS depend on treatment timing, inflammatory burden, aetiology, and biological phenotype; hyperinflammatory and hypoinflammatory subphenotypes may respond differently. [446]D
Host inflammatory and immune mechanisms
CAP severity reflects the balance between protective antimicrobial immunity and excessive or inadequately resolved inflammation. Pentraxin-3 (PTX3), mid-regional pro-adrenomedullin, and SpO2/FiO2 were evaluated longitudinally as predictors of clinical failure, illustrating the potential value of integrating inflammatory, endothelial or vascular, and respiratory measures rather than relying on one biomarker. [437] In older adults aged ≥65 years, stress hyperglycaemia was associated with delirium; neutrophil-to-lymphocyte ratio (NLR) and procalcitonin (PCT) provided only limited mediation of this relationship, suggesting that metabolic stress and inflammation are linked but not fully interchangeable mechanisms. [438]
Molecular regulation may also influence the inflammatory response. Dysregulated miR-4492 and its proposed interaction with tumour necrosis factor receptor-associated factor 6 (TRAF6) were investigated in patients with CAP and human bronchial epithelial cells, indicating a possible microRNA-mediated regulatory pathway relevant to diagnosis, prognosis, and innate immune signalling. [440] Comparative cytokine and bioinformatic analyses further indicated that CAP and COVID-19 can have divergent biological pathways despite similar plasma cytokine profiles, emphasising that cytokine concentration alone may not identify the underlying disease mechanism. [435]C
Oxidative stress, lipid metabolism, and metabolic reprogramming
Oxidative stress and inflammation are implicated in CAP pathophysiology, and hospitalized CAP patients showed altered paraoxonase-1-related variables alongside inflammatory-marker abnormalities in a prospective case-control investigation. [442] Lipidomic studies in lower respiratory tract infections identified reproducible alterations in lipid metabolism across different human infection cohorts, supporting roles for lipid mediators in host–pathogen interaction, inflammation, and biomarker development; however, heterogeneity in sample types and analytical platforms limits direct mechanistic generalisation. [82]D5
Metabolomics has also been used to explore adjunctive treatment mechanisms. A controlled before–after clinical study evaluated Pneumonia Compound Formulation combined with antibiotics against antibiotics alone in 100 CAP patients and used metabolomic analysis to investigate biological effects, but the available evidence does not establish a definitive causal metabolic pathway. [71]A1b A multicentre, double-blind randomized trial similarly evaluated standard- and low-dose Maxing Huoqiao granule as adjuncts to moxifloxacin for 7 days in adults with nonsevere CAP, with clinical outcomes and potential mechanisms assessed during a 14-day follow-up. [85]A1b These studies are hypothesis-generating for metabolic and inflammatory modulation rather than proof that either formulation reverses a specific pathogenic lesion. [71]A1b[85]A1b
Gut–lung axis and systemic inflammation
CAP is associated with gut microbial dysbiosis. Prospective sequencing studies found reduced gut-microbiota alpha diversity and distinct community composition in patients with CAP compared with healthy controls, together with systemic inflammatory changes. [441] Metagenomic and metabolomic analyses likewise identified lower microbial diversity and depletion of short-chain-fatty-acid-producing taxa, including Faecalibacterium, Ruminococcus, and Eubacterium, as well as selected species such as Faecalibacterium prausnitzii, Bifidobacterium adolescentis, Eubacterium rectale, Prevotella copri, and Ruminococcus bromii. [443] These findings support a gut–lung axis in which microbial products and metabolite availability may influence immune tone, but association studies do not prove whether dysbiosis precedes CAP, results from illness, or is modified by treatment. [441][443]
Pathogen interactions and host susceptibility
Bacterial–viral co-infection can intensify pulmonary injury and worsen prognosis. In particular, CAP involving Staphylococcus aureus with respiratory-virus co-infection has been studied as a clinically and genomically distinct process with potentially synergistic pathogenic effects. [444] Streptococcus anginosus group organisms, oral facultative anaerobes, are an underrecognized cause of pneumonia and are increasingly identified in empyema; their ability to participate in pleural infection highlights the importance of aspiration-related or polymicrobial mechanisms in selected patients. [439]C
Host susceptibility is modified by age-related immune dysfunction. Declining Th1-cell-mediated cellular immunity in older adults has been linked to weaker responses to vaccines and increased susceptibility to respiratory viral infection, providing a biological context for severe viral CAP in the elderly. [77]C4 Pathogen ecology also changes over time: Mycoplasma pneumoniae causes a broad spectrum of respiratory disease, and global resurgence during 2023–2024, together with increasing macrolide resistance, may alter the microbiological landscape and treatment pressures of CAP. [447]D
Clinical implications of mechanistic heterogeneity
Post-acute risk is not determined solely by the initial pulmonary presentation. In 7,840 CAP participants, self-organising-map clustering was used to identify high-risk clinical phenotypes for post-acute mortality, while machine-learning analyses identified predictors requiring closer follow-up. [83]B2b The emerging model of CAP therefore includes an acute pulmonary phase, systemic inflammatory and metabolic responses, possible multiorgan effects, and prolonged vulnerability after apparent clinical improvement. [83]B2b[437][438]
| Domain | Evidence and clinical relevance |
|---|---|
| Pulmonary injury | Restrictive dysfunction, ventilation–perfusion imbalance, impaired oxygenation, and possible fluid-related respiratory deterioration. [70]A1b[437][445] |
| Inflammation and immunity | PTX3, PCT, NLR, TRAF6-linked miR-4492 regulation, delirium, and heterogeneous ARDS phenotypes. [437][438][440][446]D |
| Oxidative and lipid biology | Altered PON1-related variables and lipid metabolism during lower respiratory infection. [82]D5[442] |
| Gut–lung axis | Reduced microbial diversity, altered community structure, and depletion of short-chain-fatty-acid-producing taxa. [441][443] |
| Pathogen and host interaction | Viral–S. aureus synergy, S. anginosus group empyema, immunosenescence, and M. pneumoniae resurgence or resistance. [77]C4[439]C[444][447]D |
| Recovery and prognosis | Distinct clusters may identify patients at increased post-acute mortality risk. [83]B2b |
3. Epidemiology, Etiology and Risk Factors
- ▸The supplied evidence is mainly hospital-based and cannot provide a universally applicable CAP incidence estimate. [448][449][450][451][452][459][463]
- ▸Approximately one in five hospitalized CAP patients may require ICU admission; delayed ICU admission increases risk. [449]
- ▸Respiratory pathogen patterns changed during and after the COVID-19 pandemic, requiring interpretation in relation to non-pharmacological interventions and local surveillance. [459][460]
- ▸Important pediatric pathogens in the evidence include RSV, adenovirus, human metapneumovirus, and Mycoplasma pneumoniae. [451][452][459][463]
- ▸Mycoplasma pneumoniae may show epidemics every 3–7 years; the largest annual case count in one Northeast China cohort occurred in 2023. [451]
- ▸Macrolide resistance is an increasing concern in pediatric Mycoplasma pneumoniae pneumonia. [145][454]
- ▸Type 2 diabetes was associated with higher rates of septic shock, respiratory failure, and mortality in a 2,471-patient CAP cohort. [456]
- ▸Older age, COPD with hypercapnia, and immunocompromise identify populations at increased risk of severe outcomes. [458][461][462]
Epidemiologic overview
Community-acquired pneumonia (CAP) is represented in the available evidence predominantly by hospitalized adults and children rather than population-based surveillance cohorts; therefore, these studies describe disease distribution, severity, and pathogen patterns but do not provide a generalizable incidence estimate. [448][449][450][451][452][459][463] In hospitalized CAP, approximately one in five patients may require intensive-care admission, and delayed ICU admission is associated with increased mortality risk. [449] A multicenter Italian study specifically evaluated adults hospitalized outside the ICU who nevertheless had impaired oxygenation, defined by a PaO₂/FiO₂ ratio <300, illustrating that clinically important CAP also occurs in patients not initially requiring intensive care. [450]
The epidemiology of CAP is dynamic and geographically heterogeneous. Changes in respiratory-virus transmission during the COVID-19 pandemic were associated with altered pathogen characteristics among hospitalized children with CAP in Changzhou, China, between 2018 and 2023. [459] A Sheffield, United Kingdom, study likewise examined temporal changes in sputum isolates across pre-pandemic, pandemic, and post-pandemic periods, including specimens from hospitals, primary-care settings, hospices, and palliative-care services. [460] These findings support interpreting local CAP pathogen data in the context of recent non-pharmacological interventions, healthcare-seeking patterns, and circulating respiratory viruses rather than assuming a stable pathogen distribution. [459][460]
Etiology and pathogen patterns
CAP is caused by a broad range of respiratory viruses, typical and atypical bacteria, and mixed infections. In children, the supplied studies specifically address respiratory syncytial virus (RSV), adenovirus (AdV), human metapneumovirus (hMPV), and Mycoplasma pneumoniae (MP). [451][452][459][463] A 2025 cohort of 2,315 children with CAP in Zunyi, China, evaluated RSV-, AdV-, and hMPV-associated disease and bacterial coinfection risk factors. [463] Because the available abstract does not report the adjusted risk estimates, these pathogens should be regarded as important targets for local epidemiologic assessment, while the magnitude of bacterial coinfection risk cannot be extrapolated from this study alone. [463]
Mycoplasma pneumoniae is an important pediatric CAP pathogen and may produce regional epidemics. A large retrospective cohort from Northeast China included 17,505 hospitalized MP-pneumonia cases from 2018–2023; the highest annual case count occurred in 2023, with 4,619 cases. [451] The study describes an epidemic interval of approximately 3–7 years, although the timing and intensity of epidemics may vary by region. [451] Rising macrolide resistance complicates treatment of pediatric MP pneumonia. [145]A1b[454] Molecular surveillance in Liaocheng, China, therefore combined 23S rRNA sequencing for macrolide-resistance mutations with MLVA typing in hospitalized children, while also assessing factors associated with severe disease. [454]
Targeted next-generation sequencing (tNGS) is being evaluated as a method for rapid and broad pathogen detection in pediatric CAP. A single-center study included 838 children admitted between February 2023 and May 2025 who underwent tNGS testing. [452] The study reflects increasing use of molecular diagnostics but, because it was retrospective and single-center, its pathogen frequencies should not be treated as representative of all pediatric CAP populations. [452] Rapid molecular testing was also examined in an Italian adult cohort of CAP managed outside the ICU, but the available evidence is insufficient to establish that testing changes outcomes across all healthcare settings. [450]
Legionella is a less common but potentially severe cause of CAP requiring pathogen-directed therapy. A multicenter cohort studied adults with laboratory-confirmed community-acquired Legionella pneumonia from 2019–2025 and assessed the relationship between time to effective Legionella-directed treatment and mortality. [461] The study specifically considered macrolides, fluoroquinolones, and doxycycline as effective therapies and examined whether treatment timing contributed to excess mortality among immunocompromised patients. [461]
Patient-related risk factors for severity and adverse outcomes
Older age is an important marker of poor prognosis. A prospective study enrolled 227 adults aged ≥65 years admitted to the ICU with CAP and compared SMART-COP, CURB-65, SOFA, and APACHE II for prediction of ICU mortality, intubation, vasopressor requirement, and hospital-acquired pneumonia. [458] The study emphasizes that older ICU patients represent a distinct high-risk population and that general severity scores may not have been developed specifically for this group. [458]
Type 2 diabetes mellitus (T2DM) is associated with more severe CAP and worse outcomes. In a retrospective cohort of 2,471 CAP patients, 559 (22.6%) had T2DM. Compared with patients without diabetes, those with T2DM had higher frequencies of septic shock (6.4% vs 3.5%) and respiratory failure (22.7% vs 16.5%), as well as higher mortality (8.4% vs 4.3%). [456] These observations support diabetes as a clinically relevant risk factor for organ dysfunction and death, although retrospective associations do not establish causation. [456]
Underlying chronic respiratory disease and abnormal gas exchange may further increase risk. In a dual-center study of 185 patients with acute exacerbation of chronic obstructive pulmonary disease complicated by severe pneumonia, admission hypercapnia was defined as PaCO₂ >45 mmHg and was compared with normocapnia of 35–45 mmHg and hypocapnia of <35 mmHg. [462] Hypercapnia was associated with increased ICU-admission risk and reduced inflammatory responses in this population. [462] These findings apply particularly to patients with combined COPD exacerbation and severe pneumonia, not necessarily to all CAP patients. [462]
Immunocompromise is a recognized vulnerability in Legionella CAP, particularly when effective therapy is delayed. [461] Severe CAP cohorts and treatment trials also preferentially represent patients with hospitalization, organ dysfunction, or ICU-level illness, limiting direct application of their findings to ambulatory CAP. [125]A1a[146]A1a[449][450][453][457] Pediatric studies similarly focus largely on hospitalized or clinically selected populations, so risk estimates should be interpreted according to age, setting, comorbidity, and local pathogen circulation. [145]A1b[451][452][454][459][463]
Practical epidemiologic interpretation
The most useful risk assessment combines host factors—especially advanced age, T2DM, COPD with hypercapnia, and immunocompromise—with current respiratory-virus activity, local MP resistance patterns, recent pandemic-related transmission changes, and the possibility of atypical or mixed infection. [145]A1b[451][454][456][459][460][461][462] Local surveillance remains essential because the available studies are geographically concentrated and predominantly retrospective or hospital-based. [450][451][452][454][456][459][460][463]
| Domain | Evidence | Clinical interpretation |
|---|---|---|
| ICU risk | Approximately one in five CAP patients may require ICU admission. [449] | Monitor early for organ dysfunction and deterioration. |
| Pediatric MP epidemiology | 17,505 hospitalized cases from 2018–2023; 4,619 cases occurred in 2023; reported epidemic interval 3–7 years. [451] | Expect substantial temporal and regional variation. |
| Diabetes | T2DM: septic shock 6.4% vs 3.5%, respiratory failure 22.7% vs 16.5%, mortality 8.4% vs 4.3%. [456] | T2DM is associated with increased severity and mortality. |
| COPD and gas exchange | Hypercapnia defined as PaCO₂ >45 mmHg was associated with increased ICU-admission risk in AECOPD with severe pneumonia. [462] | Hypercapnia should heighten concern for escalation. |
| Older adults | Study of 227 ICU patients aged ≥65 years assessed mortality, intubation, vasopressor use, and hospital-acquired pneumonia. [458] | Older ICU patients require age-appropriate severity assessment. |
| Immunocompromise | Legionella cohort evaluated whether delayed effective therapy contributed to excess mortality among immunocompromised patients. [461] | Consider Legionella and prompt targeted therapy when clinically indicated. |
4. Clinical Presentation
- ▸CAP presentation is nonspecific; emergency-department diagnosis may be discordant with the eventual diagnosis, so assessment should combine clinical, laboratory, imaging, and vital-sign data [466].
- ▸In a non-ICU hospitalized cohort, clinically significant oxygenation impairment was defined by a **PaO₂/FiO₂ ratio <300** [450].
- ▸Severe Chlamydia psittaci pneumonia models identify severity at presentation rather than predict progression, and the available evidence is hypothesis-generating [210].
- ▸Children with viral, Mycoplasma pneumoniae, and mixed-pathogen CAP may have overlapping presentations; co-detection and extrapulmonary manifestations can modify the clinical phenotype [213] [222] [467] [469].
- ▸Pleural complications, including pyopneumothorax, should prompt consideration of unusual organisms and relevant exposure or dental history [465].
4.1 General presentation and diagnostic uncertainty
Community-acquired pneumonia (CAP) is clinically heterogeneous, and its manifestations may overlap with other respiratory infections and noninfectious conditions. In an emergency-department cohort of 1,385 adults initially diagnosed with CAP, investigators specifically evaluated diagnostic concordance, alternative discharge diagnoses, and the clinical, laboratory, imaging, and vital-sign features associated with confirmed CAP, underscoring that an initial clinical label may not always represent pneumonia [466]. Clinical assessment should therefore integrate symptoms, vital signs, oxygenation, examination, laboratory findings, and chest imaging rather than relying on a single feature [466].
4.2 Adults hospitalized outside the ICU
The Italian SIS-NET study prospectively characterized 176 adults hospitalized with CAP outside the ICU who had a PaO₂/FiO₂ ratio <300, indicating clinically important impairment of oxygenation in this cohort [450]. The study collected demographic, clinical, laboratory, radiological, microbiological, treatment, and outcome data and evaluated rapid syndromic respiratory panels in a subset of patients [450]. These findings support describing hospitalized non-ICU CAP according to the combined burden of respiratory impairment, radiological disease, systemic findings, and microbiological features rather than by symptoms alone [450].
Rapid molecular testing may alter the characterization of presentation because it can identify respiratory pathogens in patients whose routine evaluation is unrevealing; however, the SIS-NET study assessed its effect on hospital outcomes, not merely diagnostic yield [450]. A separate retrospective comparison of targeted next-generation sequencing (tNGS) with conventional tests analyzed 380 bronchoalveolar-lavage-fluid samples from patients with CAP or severe CAP, reflecting the use of lower-respiratory-tract sampling when disease severity or diagnostic uncertainty warrants more intensive investigation [211]B2b.
4.3 Features associated with severe disease
Severity assessment should distinguish patients who are already severely ill at presentation from those at risk of later deterioration. In patients with confirmed Chlamydia psittaci pneumonia, a small double-center retrospective study emphasized that its proposed creatine-kinase/direct-bilirubin model was designed to identify severe pneumonia at presentation, not to predict progression from non-severe disease [210]B2b. Because only 36 hospitalized patients were included, with 11 classified as severe and 25 as non-severe, the model is hypothesis-generating and should not replace established clinical assessment [210]B2b.
Psittacosis may produce systemic manifestations and multi-organ dysfunction in addition to pulmonary disease, which may be particularly relevant when the respiratory presentation is accompanied by disproportionate biochemical abnormalities or a compatible zoonotic exposure history [210]B2b. In a temporally associated series of four non-severe patients, bronchoalveolar-lavage-fluid tNGS was used to detect C. psittaci in a resource-limited county hospital, illustrating that an atypical or epidemiologically clustered presentation may require specialized testing [267]C4.
Legionella pneumonia is another CAP presentation that can require pathogen-directed therapy; a multicenter cohort studied adults with laboratory-confirmed community-acquired Legionella pneumonia and examined the interval from presentation to effective treatment and its relationship with mortality [461]. The study included macrolides, fluoroquinolones, and doxycycline as effective Legionella-directed therapies, but the treatment-timing findings should be interpreted as outcome evidence rather than as a symptom-based diagnostic rule [461].
4.4 Pediatric CAP and pathogen-specific phenotypes
Pediatric CAP may present with overlapping clinical syndromes that make etiologic differentiation difficult. A study of hospitalized children with human metapneumovirus-positive CAP compared 632 mild and 246 severe cases and evaluated demographic, clinical, and laboratory characteristics and independent risk factors for severe disease [213]B2b. The investigators noted that human metapneumovirus presentation closely resembles that of other common respiratory viruses, making clinical diagnosis alone challenging [213]B2b. Similarly, a biomarker-signature study addressed the difficulty of distinguishing respiratory syncytial virus from Mycoplasma pneumoniae because both can cause overlapping respiratory symptoms in children with CAP [469].
Among children with M. pneumoniae pneumonia, a randomized multicenter trial enrolled 160 children aged 4–14 years with mild disease and evaluated adjunctive Lianhua Qingke tablets during 7 days of conventional therapy [145]A1b. The trial’s population represents a mild pediatric M. pneumoniae phenotype rather than severe CAP, and its primary relevance to presentation is the recognition of M. pneumoniae as an important pediatric CAP cause in the context of increasing macrolide resistance [145]A1b.
M. pneumoniae may also cause extrapulmonary mucocutaneous disease. A systematic review and case series examined M. pneumoniae-associated oral mucositis and the clinical entity of M. pneumoniae-induced rash and mucositis (MIRM), assessing reported clinical features, diagnostic criteria, and outcomes from studies published between 2015 and 2025 [222]B2a. Prominent mucositis, particularly when accompanied by limited cutaneous disease, should therefore prompt consideration of an extrapulmonary M. pneumoniae complication rather than being treated as an uncomplicated respiratory presentation [222]B2a.
4.5 Coinfection and uncommon complications
Respiratory-pathogen co-detection is common enough in hospitalized pediatric M. pneumoniae pneumonia to warrant explicit assessment: in a cohort of 3,081 children, 1,173 had monoinfection and 1,908 had co-detection [467]. The study evaluated associations with severe M. pneumoniae pneumonia, complications, healthcare utilization, and costs, indicating that co-detection may be clinically relevant to the severity phenotype [467]. Unsupervised clustering research further classified pediatric CAP using microbiological findings from bronchoalveolar lavage, inflammatory response, and clinical characteristics, reflecting substantial heterogeneity beyond a single-pathogen label [432].
Empyema and pyopneumothorax are severe pediatric complications of CAP. A case report described a 10-year-old with bilateral pneumonia and pyopneumothorax caused by the anaerobe Prevotella oris after tooth extraction 1 week before symptom onset, illustrating the importance of dental or aspiration-related history when chest pain or pleural complications accompany pneumonia [465].
Frank’s sign, an acquired diagonal earlobe crease, was investigated as a marker associated with cardiovascular events after pneumonia in a prospective cohort of adults hospitalized with CAP and followed for 18 months [212]B2b. The composite cardiovascular outcome included new atrial fibrillation/flutter and myocardial infarction, suggesting that cardiovascular risk assessment may be relevant during and after hospitalization, although Frank’s sign is not a diagnostic feature of CAP [212]B2b.
| Clinical context | Presentation-related implication | Evidence |
|---|---|---|
| Hospitalized CAP outside ICU | Assess oxygenation, radiology, laboratory findings, microbiology, and outcomes together; PaO₂/FiO₂ <300 characterized the studied cohort | [450] |
| Suspected C. psittaci pneumonia | Consider systemic or multi-organ involvement and zoonotic exposure; proposed biomarkers identify severity at presentation | [210]B2b [267]C4 |
| Pediatric M. pneumoniae pneumonia | May occur as mild CAP in children aged 4–14 years; extrapulmonary mucositis may indicate MIRM | [145]A1b [222]B2a |
| Pediatric CAP with co-detection | Mixed respiratory pathogens may be associated with a distinct severity and complication phenotype | [432] [467] |
| Pneumonia with pleural air and pus | Consider empyema or pyopneumothorax and uncommon anaerobic pathogens, particularly with recent dental history | [465] |
5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored)
- ▸Chest radiograph remains the first-line confirmatory test, but CT identifies infiltrates in one-third of patients with negative radiographs and changes management in nearly 60%.
- ▸Pneumococcal urinary antigen is highly specific (99.7%) and increases pathogen identification by nearly 40%; targeted NGS from BALF offers superior clinical consistency for severe or refractory cases.
- ▸Blood cultures and respiratory PCR should be targeted to hospitalized or severe CAP; bronchoscopy is reserved for immunocompromised hosts, treatment failure, or suspected noninfectious mimics.
The clinical features described in the preceding section raise suspicion for community-acquired pneumonia (CAP); confirmation requires radiographic evidence of an acute pulmonary infiltrate supported by microbiologic and laboratory studies. The diagnostic approach balances test performance, patient severity, and resource availability, guided by the 2019 ATS/IDSA and 2026 updated guidelines [2]A1c[1]A1c[20]D5.
Imaging - The Initial Anchor
A chest radiograph remains the first-line test to confirm parenchymal involvement. A discrete infiltrate (lobar, multilobar, or interstitial) establishes the diagnosis. However, chest radiograph misses up to 33% of infiltrates: in one prospective study of 319 patients with suspected CAP, CT revealed an infiltrate in 40 of 120 patients (33%) with a negative radiograph, and excluded CAP in 56 of 188 patients (30%) with a positive one [4]B2b. Early multidetector chest CT modified diagnosis and in 58.6% (95% CI 53.2-64.0), leading to antibiotic initiation in 16% and discontinuation in 9% [4]B2b. CT is not routine for all patients but is indicated when the diagnosis is uncertain, complications (empyema, abscess) are suspected, or the patient fails to improve. Dominant HRCT patterns include consolidation, ground-glass opacity, and centrilobular nodules; specific patterns may hint at atypical pathogens (e.g., tree-in-bud for Mycoplasma or viral) [251]C4. The 2025 ATS guideline also supports lung ultrasound for diagnosis when performed by experienced clinicians, especially in emergency and critical care settings [20]D5[240]B2b.
Laboratory Biomarkers
Biomarkers support diagnosis and severity assessment but are not diagnostic alone. C-reactive protein (CRP) and procalcitonin (PCT) levels vary with time from symptom onset: in early presenters (<3 days), CRP is lower and PCT higher; in later presenters (≥3 days), CRP rises by 36-38% and PCT falls by 40-56% [184]B2b. In patients with emphysema, median CRP and PCT are significantly lower (CRP 116 vs. 254 mg/L), potentially masking infection [263]C4. A PCT threshold <0.25 ng/mL can help defer in low-risk outpatients with low clinical suspicion.
Microbiologic Testing
Causative pathogen identification guides targeted therapy and is particularly important in moderate-to-severe CAP.
| Test | Sensitivity | Specificity | Key Indication |
|---|---|---|---|
| Blood culture | ~10% positivity in hospitalized CAP [236]B2b | High | Severe CAP, ICU admission, prior antibiotic failure |
| Sputum Gram stain + culture | Variable (quality-dependent) | ~80% when adequate specimen | Hospitalized patients with productive cough |
| Pneumococcal urinary antigen | 60-75% [228]B2a[259]B2b | 99.7% [259]B2b | All hospitalized CAP (rapid, noninvasive) |
| Legionella urinary antigen | ~70% for serogroup 1 | >99% | Severe CAP, ICU, travel/cluster history |
| Multiplex PCR (nasopharyngeal swab) | 80-95% for viruses/atypicals [229]B3b[247]B2b | High | Immunocompromised, ICU, epidemiologic context |
| Targeted NGS (BALF) | 83% clinical consistency [211]B2b | 82% [211]B2b | Severe/refractory CAP, suspected rare pathogens |
Blood cultures are positive in approximately 10% of hospitalized CAP and are recommended for patients with severe disease (ICU admission, septic shock) [236]B2b. Independent predictors of bacteremia include pleuritic pain, CRP ≥21.6 mg/dL, and ICU admission [236]B2b. Urinary antigen testing for pneumococcus dramatically increases identification of pneumococcal CAP, by 39% in one study, and may allow streamlining to β-lactam monotherapy when positive, given its near-perfect specificity [238]B2b[259]B2b. The test is more likely positive in patients with higher severity (low blood pressure, tachypnea, hypoxemia) and less likely if prior antibiotics were given [259]B2b. Tracheal aspirate culture in intubated patients identifies a pathogen in 56% and provides the sole positive result in 39% of cases [46]B3b. Targeted next-generation sequencing (tNGS) from bronchoalveolar lavage fluid (BALF) shows superior clinical consistency (83% vs. 38% for conventional tests) and detects resistance genes [211]B2b. In resource-limited settings, outsourcing BALF-tNGS to a central lab can still yield a rapid diagnosis [267]C4.
Diagnostic Bronchoscopy
Flexible bronchoscopy with bronchoalveolar lavage is reserved for patients who fail to stabilize, are immunocompromised, or have suspected noninfectious mimics. BAL with quantitative cultures has a diagnostic yield of up to 70% when routine tests are negative [130]D5. In solid organ transplant recipients with CAP, bronchoscopy within 24 hours significantly increased the odds of establishing an etiology [243]B2b. Transbronchial biopsy and EBUS-TBNA are rarely needed for typical CAP but may be indicated for suspected granulomatous disease (e.g., tuberculosis, fungal) or malignancy causing post-obstructive pneumonia [268]C4. Therapeutic bronchoscopy is addressed in Section 9.
Arterial Blood Gas
ABG is essential for assessing gas exchange: a PaO₂/FiO₂ ratio <300 defines hypoxemic respiratory failure and upgrades severity [186]B2b. Hypercapnia (PaCO₂ >45 mmHg) signals ventilatory failure, often in patients with underlying . ABG also guides decisions for admission, oxygen therapy, and noninvasive ventilation.
Spirometry and lung volumes are not indicated during the acute phase of CAP. They may be performed 4-6 weeks after resolution to evaluate residual restrictive defects (reduced FVC, TLC) or persistent obstructive physiology, particularly in patients with COPD. DLCO is not routinely measured.
Diagnostic Algorithm
Step 1: Clinical suspicion (cough, fever, dyspnea, focal signs) → Obtain chest radiograph. If infiltrate present, diagnosis confirmed. If radiograph negative but clinical suspicion high, consider chest CT or lung ultrasound. Step 2: Assess severity (see Section 6) to determine site of care (outpatient, ward, ICU). Step 3: In hospitalized patients, obtain blood cultures (×2), sputum culture (if purulent), pneumococcal and Legionella urinary antigen, and respiratory viral PCR. In severe or ICU CAP, add legionella culture on BAL or sputum and consider tNGS if initial tests are negative. Step 4: If no response at 48-72 hours, repeat blood cultures, chest CT, and proceed to bronchoscopy with BAL ± tNGS. Step 5: For immunocompromised patients or those with structural lung disease, consider bronchoscopy earlier with BAL for fungal, mycobacterial, and viral studies.
Controversies and Guideline Disagreement
| Question | Position A | Position B | Strength | Implication |
|---|---|---|---|---|
| Role of routine blood cultures | ATS/IDSA 2019: recommend only for severe CAP [2]A1c | NICE 2014: limited role in nonsevere CAP [249]D5 | Moderate | Blood cultures should not be obtained in low-risk outpatients but are essential in ICU patients. |
| Use of procalcitonin to guide antibiotic initiation | 2025 ATS update: consider in low-risk outpatients [20]D5 | ESCMID/ERS: not routinely recommended [119]A1c | Weak | PCT can support de-escalation but should not replace clinical judgment. |
Pearl: In early presenters (<3 days of symptoms), CRP may be misleadingly low and PCT may be high, do not rule out CAP based on a single biomarker level; use the combination of a negative radiograph and a very low PCT (<0.1 ng/mL) to safely withhold antibiotics [184]B2b[20]D5.
6. Severity, Staging and Risk Stratification
- ▸Use repeated clinical assessment because CAP severity can evolve after admission, and conventional scores may miss early organ dysfunction [449].
- ▸Operational staging distinguishes mild disease without oxygen, moderate disease requiring ward oxygen, and severe disease requiring high-dependency or ICU care [470].
- ▸PaO₂/FiO₂ <300, hypercapnia >45 mmHg, shock, rising oxygen requirements, or organ dysfunction should prompt urgent reassessment for higher-acuity care [450][462].
- ▸SMART-COP, CURB-65, SOFA, and APACHE II have different purposes and populations; no single score should replace clinical judgment [458].
- ▸Diabetes, immunocompromise, pathogen-specific factors, inflammatory biomarkers, transcriptomics, and CT burden can modify risk [278][425][449][456][461].
Scope and principles
Severity assessment in community-acquired pneumonia (CAP) should be dynamic and should combine bedside physiology, organ dysfunction, oxygenation, comorbidity, radiographic burden, microbiology, and trajectory rather than relying on a single score. Contemporary cohorts continue to identify a substantial subgroup at risk for ICU admission, organ dysfunction, respiratory failure, vasopressor use, and death, including patients who do not initially appear critically ill [449]. Risk classification should therefore be repeated after initial resuscitation, oxygen escalation, development of shock, or deterioration in mental status [449].
Initial clinical staging
A practical clinical staging approach is:
- Mild CAP: managed on a general ward without supplemental oxygen.
- Moderate CAP: managed on a general ward but requiring supplemental oxygen.
- Severe CAP: requiring high-dependency or ICU-level care [470].
This staging is operational rather than a replacement for validated prognostic scores. Oxygenation is particularly important: in a prospective Italian cohort of adults treated outside the ICU, all participants had a PaO₂/FiO₂ ratio <300, demonstrating that clinically significant gas-exchange impairment may be present even when ICU care is not initially required [450]. Hypercapnia may further increase risk in patients with acute exacerbation of chronic obstructive pulmonary disease and severe pneumonia; in a retrospective cohort, admission PaCO₂ was categorized as >45 mmHg, 35–45 mmHg, or <35 mmHg, with hypercapnia associated with increased ICU-admission risk and altered inflammatory responses [462].
Validated scores and disposition
CURB-65 remains useful for initial mortality and disposition assessment, but it should not be used in isolation when there is hypoxemia, rapidly increasing oxygen need, shock, severe acidosis, hypercapnia, multilobar disease, or major comorbidity [458]. In older adults already admitted to the ICU, SMART-COP was specifically evaluated against CURB-65, SOFA, and APACHE II for ICU mortality, intubation, vasopressor requirement, and hospital-acquired pneumonia; this study highlights that scores developed in general CAP populations may have limited applicability in older ICU patients [458]. SOFA and APACHE II may better characterize established organ dysfunction in critical care, whereas SMART-COP provides pneumonia-specific information about the likelihood of intensive respiratory or circulatory support [458].
The need for ICU review should be driven by actual support requirements and trajectory, not solely by a numerical score. Delayed ICU admission is associated with increased risk in hospitalized patients who subsequently develop organ dysfunction, and conventional clinical scores may miss early progression [449].
Biomarkers and emerging prediction tools
Biomarkers can refine, but should not replace, clinical assessment. In hospitalized adults, urinary soluble urokinase plasminogen activator receptor (suPAR) and neutrophil gelatinase-associated lipocalin (NGAL) were prospectively evaluated across mild, moderate, and severe CAP strata; these markers were associated with disease severity and microbiological characteristics, supporting urinary biomarkers as potential adjuncts for identifying patients at risk for higher-acuity care [470].
A five-gene blood transcriptomic signature was developed from 455 participants across 41 centers in the PROGRESS cohort to identify patients at risk for organ dysfunction and death. Its clinical rationale is that molecular disease-course prediction may improve on conventional scores and routine metrics, although it should be regarded as an emerging tool pending broad external implementation and outcome validation [449].
In children younger than 5 years, admission inflammatory phenotyping using neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, systemic immune-inflammation index, systemic inflammation response index, C-reactive protein, and procalcitonin was investigated for prediction of severe CAP and pediatric acute respiratory distress syndrome (PARDS) [425]. A separate pediatric nomogram study used clinical, laboratory, and etiological variables to predict severe CAP and reported discrimination and calibration assessment, but its single-center retrospective design limits immediate generalization [471].
Comorbidity, etiology and imaging modifiers
Risk is modified by host factors. In a cohort of 2,471 adults, type 2 diabetes was associated with more septic shock (6.4% vs 3.5%), respiratory failure (22.7% vs 16.5%), and mortality (8.4% vs 4.3%) compared with non-diabetes [456]. Immunocompromised patients with Legionella pneumonia may also be vulnerable to delayed effective therapy; effective treatment included a macrolide, fluoroquinolone, or doxycycline, and time to effective therapy was examined in relation to mortality [461].
Etiology can influence severity and the urgency of targeted treatment. In children with Mycoplasma pneumoniae pneumonia, a large retrospective series evaluated adverse outcomes and associated factors across 2018–2023, while a 2023–2024 study assessed inflammatory markers, macrolide-resistance mutations, and MLVA profiles as predictors of severe disease [451][454]. Targeted next-generation sequencing was evaluated in 838 children as a method for more comprehensive pathogen detection, potentially supporting earlier etiologic risk assessment, although diagnostic detection alone does not establish clinical severity [452].
Radiographic burden may add prognostic information in selected infections. In 69 patients with Chlamydia psittaci pneumonia, CT-based scores quantified lobar and segmental involvement: the chest CT score ranged from 0–25 and the CT severity score from 0–40; both were assessed for association with ICU admission [278]B2b. Rapid molecular diagnostics were also studied in adults managed outside the ICU, including their relationship to hospital outcomes and time to live discharge [450].
Treatment-related severity considerations
Adjunctive low-dose corticosteroids have been studied in adults with severe pulmonary infections, including CAP, sepsis, septic shock, and ARDS, with short-term mortality through 90 days as the primary outcome in a 2026 meta-analysis [125]A1a. A network meta-analysis of 32 randomized trials involving 9,746 hospitalized CAP patients compared dexamethasone-equivalent high-dose therapy (≥7.5 mg/day) with lower-dose therapy (<7.5 mg/day) for short-term mortality; dose selection should therefore be considered separately from the decision to use corticosteroids at all [146]A1a.
Short-course antibiotic therapy (≤5 days) has been compared with longer courses (>5 days) in adult CAP randomized trials, primarily evaluating clinical success and severe adverse events; duration should be individualized according to clinical stability and severity rather than determined solely at admission [448].
| Domain | Higher-risk findings | Evidence |
|---|---|---|
| Care requirement | High-dependency or ICU requirement | [470] |
| Oxygenation | PaO₂/FiO₂ <300; escalating oxygen need | [450] |
| Ventilation | PaCO₂ >45 mmHg, particularly with AECOPD and severe pneumonia | [462] |
| Circulation/organ function | Shock, vasopressor requirement, respiratory failure, or evolving organ dysfunction | [449][456][458] |
| Host factors | Older age, type 2 diabetes, or immunocompromise | [456][458][461] |
| Emerging adjuncts | Urinary suPAR/NGAL, five-gene signature, inflammatory phenotypes, or CT severity scores | [278]B2b[425][449][470] |
7. Acute Management and Exacerbation Rescue
- ▸Use repeated clinical assessment and early escalation for hypoxaemia, respiratory distress, hemodynamic instability, altered mental status, or worsening gas exchange. [450][462][473]
- ▸In adults with CAP, PaO₂/FiO₂ <300 identifies a high-risk hospitalized population; in the betamethasone trial, hypoxaemia was defined as SpO₂ <93% with respiratory rate >20/min. [450][473]
- ▸Use MDRO risk assessment and rapid diagnostics to support targeted empiric therapy and de-escalation rather than reflexive extended-spectrum treatment. [133][450][464]
- ▸In selected African children aged 2 months to 6 years with severe uncomplicated CAP, PediCAP directly supports evaluation of oral step-down therapy and shorter treatment strategies after initial intravenous treatment. [472]
- ▸Corticosteroids should be individualized; evidence includes a large adult meta-analysis and a Mycoplasma pneumoniae-specific betamethasone trial, but does not justify universal use. [473][474]
- ▸Ivermectin, pentoxifylline, photobiomodulation, omega-3 supplementation, Lianhua Qingke, and omadacycline lack sufficient evidence for routine CAP rescue use. [300][301][70][477][145][475]
Immediate assessment and escalation
Acute management should begin with confirmation that the presentation is compatible with CAP while actively considering alternative diagnoses, because emergency-department diagnostic discordance is common and CAP features overlap with other conditions. [466] Reassess respiratory rate, work of breathing, oxygenation, mental status, perfusion, blood pressure, gas exchange, and the need for organ support at presentation and repeatedly during the first hours of treatment. [450][470] In adults with CAP, hypoxaemia and a PaO₂/FiO₂ ratio <300 identify a clinically important population requiring close monitoring, even when managed outside the ICU. [450] Hypercapnia in patients with acute exacerbation of COPD complicated by severe pneumonia is associated with increased ICU-admission risk and reduced inflammatory responses; these patients warrant early consideration of higher-level respiratory support and ICU review. [462]
Risk scores may support, but should not replace, bedside assessment. CURB-65 augmented with the neutrophil-to-lymphocyte ratio improved identification of older adults at high risk of 30-day mortality in an emergency setting, particularly in age-stratified analyses. [478]C In patients with severe CAP, combining CURB-65 with the platelet-to-lymphocyte ratio was also evaluated as a mortality-prediction strategy. [479] These observational findings support using hematologic indices as adjuncts rather than as stand-alone triggers for admission, ICU transfer, or treatment limitation. [478]C[479]
Antimicrobial treatment and de-escalation
Start empiric antibacterial treatment promptly when bacterial CAP is clinically suspected, then adapt therapy to microbiology, local resistance patterns, organ function, allergy history, and clinical response. The Italian SIS-NET cohort assessed rapid syndromic respiratory diagnostics in hospitalized adults with CAP managed outside the ICU, supporting their potential role in refining microbiological diagnosis and treatment decisions, although the available abstract does not establish a universal outcome benefit. [450] The RESPIRE score was derived and validated to identify adults with CAP caused by resistant pathogens in a medium-to-high multidrug-resistant setting; such tools may help target extended-spectrum empiric therapy, but external validation is required before routine adoption elsewhere. [464]
Antibiotic stewardship is particularly important in patients with cancer. In the INSPIRE cluster-randomized trials, computerized prescribing prompts supplied patient- and pathogen-specific multidrug-resistant-organism risk estimates to inform empiric antibiotic selection in non-critically ill hospitalized adults with cancer. [133]B2b This evidence supports structured risk-based selection rather than automatic use of extended-spectrum antibiotics when the individual risk of an MDRO is low. [133]B2b
For African children aged 2 months to 6 years hospitalized with severe, uncomplicated CAP, the PediCAP factorial randomized trial directly evaluated intravenous-to-oral step-down therapy and shorter treatment durations. [472] Eligible children weighed 3–30 kg and had point-of-care C-reactive protein >10 mg/L; the trial compared oral amoxicillin with co-amoxiclav after intravenous therapy. [472] These results are directly relevant to clinically improving children who can absorb oral medication, but should not be generalized to children with complications, treatment failure, severe immunosuppression, or a different epidemiologic setting without clinical judgment. [472]
Oxygen, respiratory support, and supportive care
Provide oxygen and escalate respiratory support according to oxygenation, work of breathing, gas exchange, hemodynamics, and trajectory rather than a single measurement. Adults with hypoxaemic CAP were specifically studied in a randomized trial of adjunctive betamethasone, with eligibility defined by oxygen saturation <93% and respiratory rate >20 breaths/min. [473] These thresholds identify a trial population, not a universal oxygen-prescription target. [473]
Investigational supportive interventions should not displace established respiratory and antimicrobial care. A small randomized trial of infrared photobiomodulation added to conventional therapy in 30 patients reported assessment of cardiopulmonary and hematologic outcomes, but its sample size and intervention-specific design do not establish routine use. [70]A1b A pilot study of enteral omega-3 fatty acids in 84 patients with severe pneumonia reported reductions in mechanical-ventilation duration and hospital costs, without the anticipated anti-inflammatory effect; the findings remain preliminary. [477]C
Corticosteroids and adjunctive rescue therapies
Systemic corticosteroids remain a selective adjunct rather than routine treatment for every patient with CAP. An updated meta-analysis of 20 randomized trials involving 5,866 adults evaluated mortality and morbidity outcomes with corticosteroids versus placebo or usual care, reflecting persistent uncertainty about universal use. [474] In a randomized trial of hypoxaemic adults with Mycoplasma pneumoniae CAP, oral betamethasone was administered at 3 mg daily on days 1–2, followed by 2 mg daily on days 3–5; patients with asthma or diabetes were excluded, so applicability to those groups is uncertain. [473] Observational comparison of hydrocortisone and methylprednisolone cannot establish that one corticosteroid is superior because treatment allocation was non-randomized. [457]
Do not use ivermectin as routine treatment for hospitalized COVID-19 pneumonia on the basis of the REMAP-CAP platform trial; the study compared ivermectin with no ivermectin in critically and noncritically ill patients, but the available abstract does not report a positive efficacy result supporting routine adoption. [300]A1b Similarly, oral pentoxifylline, tested as an adjunct in 106 hospitalized children, remains investigational pending confirmation of clinically meaningful benefit and safety in larger studies. [301]A1b Lianhua Qingke tablets were studied for 7 days with conventional therapy in 160 children aged 4–14 years with mild Mycoplasma pneumoniae pneumonia; this evidence does not establish a rescue role in severe CAP. [145]A1b
For macrolide-unresponsive Mycoplasma pneumoniae pneumonia, intravenous omadacycline was retrospectively compared with continued azithromycin in 64 hospitalized children aged 8–16 years after persistent fever for >72 hours of azithromycin monotherapy. [475]C Because treatment was non-randomized and pediatric safety and dental/bone considerations require particular caution, omadacycline should not be considered routine rescue therapy solely from this study. [475]C
Reassessment and treatment failure
Failure to improve should prompt reassessment of diagnosis, complications, resistant or atypical pathogens, adherence or absorption, drug toxicity, extrapulmonary infection, and noninfectious mimics. [466][464] Urinary suPAR and NGAL were prospectively evaluated as severity and etiologic biomarkers in 506 hospitalized adults, but these tests should be regarded as risk-stratification research rather than replacements for clinical assessment and standard investigations. [470] Novel laboratory ratios and biomarkers may refine prognosis, but they do not independently determine antimicrobial choice or ICU disposition. [478]C[479]
| Clinical decision | Evidence-informed approach | Evidence |
|---|---|---|
| Severity and disposition | Combine bedside findings with oxygenation, gas exchange, organ-support needs, and validated risk tools; CURB-65 plus NLR or PLR may improve mortality-risk stratification but is not a stand-alone disposition rule. | [450][462][478]C[479] |
| Empiric antibiotics | Select therapy using local epidemiology, patient-specific MDRO risk, microbiology, and rapid diagnostics; avoid automatic extended-spectrum coverage in low-risk cancer patients. | [133]B2b[450][464] |
| Pediatric step-down | In selected children with severe uncomplicated CAP, assess transition from intravenous therapy to oral amoxicillin or co-amoxiclav when clinically appropriate. | [472] |
| Corticosteroids | Consider selectively in severe or hypoxaemic disease; do not infer superiority of hydrocortisone over methylprednisolone from retrospective data. | [473][474][457] |
| Suspected treatment failure | Reassess diagnosis, complications, resistance, absorption, adherence, and noninfectious mimics before escalating treatment. | [466][464] |
8. Long-term and Definitive Management
- ▸Use pathogen-directed, susceptibility-guided therapy and step down from intravenous to oral treatment when clinically appropriate; PediCAP specifically evaluated oral amoxicillin or amoxicillin-clavulanate and shorter treatment in young children with severe uncomplicated CAP. [472]
- ▸Avoid routine broad-spectrum antibiotics; patient-specific MDRO-risk tools and the RESPIRE score may support more precise empiric selection. [133][464]
- ▸Do not use corticosteroids, ivermectin, intensified heparin, photobiomodulation, or complementary tablets routinely without a defined indication and evidence applicable to the individual patient. [95][145][300][304][480]
- ▸Long-term follow-up should consider cardiovascular and thromboembolic complications, functional and social vulnerability, and mortality risk through 1 year. [12][482][483]
- ▸Review vaccination and preventive care, particularly influenza vaccination strategies in adults aged **≥65 years**. [302]
Completing antimicrobial therapy
Definitive antibiotic management should be guided by the identified pathogen, susceptibility results, clinical response, and the patient’s risk of multidrug-resistant organisms (MDROs), while avoiding unnecessarily broad or prolonged therapy. In hospitalized adults with cancer, the INSPIRE trials evaluated computerized prescribing prompts that supplied patient- and pathogen-specific MDRO-risk estimates to reduce empiric extended-spectrum antibiotic use; this addresses the common mismatch between frequent broad-spectrum prescribing and the generally low prevalence of MDROs in this population. [133]B2b A validated RESPIRE score has also been derived and prospectively validated to predict CAP caused by resistant pathogens in adults with microbiologically confirmed disease, although its applicability depends on local epidemiology and external validation. [464]
For children aged 2 months to 6 years hospitalized with severe, uncomplicated CAP, the PediCAP factorial randomized trial directly evaluated intravenous-to-oral step-down therapy with amoxicillin or amoxicillin-clavulanate and investigated the shortest effective total treatment duration. [472] These findings are particularly relevant to discharge planning because they test whether clinically improving children can safely transition from intravenous therapy rather than completing a prolonged intravenous course; treatment duration should nevertheless follow the trial-supported regimen, clinical response, and local pediatric guidance. [472] In elderly adults, omadacycline was compared with moxifloxacin in a randomized trial and was reported as non-inferior for CAP treatment, supporting it as a potential alternative when clinically appropriate, although the small study included 97 participants and should not replace pathogen-directed selection or consideration of drug-specific risks. [337]A1b
Stewardship decisions should incorporate probability-based interpretation of diagnostic tests. A pragmatic randomized trial evaluated an electronic stewardship note that interpreted low procalcitonin or a positive respiratory-virus test in terms of the post-test probability of bacterial pneumonia and linked that interpretation to antibiotic decisions. [306]A1b In outpatient suspected CAP, a randomized digital vignette study compared clinical assessment alone with chest radiography, C-reactive protein (CRP), or both to determine whether testing reduces antibiotic initiation; this supports selective use of objective testing when the diagnosis or need for antibiotics is uncertain rather than automatic treatment of every respiratory illness. [305]C4
Adjunctive therapies and treatments not routinely indicated
Adjunctive corticosteroids should not be used routinely for all CAP. A pragmatic randomized trial in 2,180 adults in Kenyan public hospitals assessed 10 days of low-dose oral glucocorticoids in patients without another clear steroid indication, reflecting the uncertainty of benefit in resource-limited settings. [95]A1b In children with severe CAP, a double-blind randomized trial evaluated 5 days of intravenous dexamethasone in addition to antimicrobials, with treatment failure at 72 hours as the primary outcome and respiratory failure, ventilation, shock, mortality, hospital stay, readmission, and inflammatory markers as secondary outcomes. [480] Steroids should therefore be reserved for a defined indication or a carefully selected severe inflammatory phenotype, with monitoring for adverse effects and recognition that evidence differs by age, severity, etiology, and healthcare setting. [95]A1b[480]
For severe COVID-19 pneumonia requiring respiratory support, early CRP reduction during glucocorticoid treatment was associated with survival in a re-analysis of the MEDEAS randomized trial; this is prognostic evidence and does not establish that escalating steroids solely to lower CRP improves outcomes. [481] In critically ill patients with COVID-19, an adaptive randomized trial compared intermediate-dose with standard low-dose heparin thromboprophylaxis for up to 14 days in hospital, using organ-support-free days as the primary endpoint; anticoagulation intensity should therefore be individualized rather than automatically increased for CAP or COVID-19. [304]A1b Ivermectin was evaluated against no ivermectin in critically and noncritically ill hospitalized patients with COVID-19 in the REMAP-CAP adaptive platform trial, with organ-support-free days through day 21 as the primary outcome; it should not be added to standard CAP management without evidence of benefit and a specific indication. [300]A1b
Photobiomodulation using a 940-nm infrared LED vest for 15 minutes daily for 7 days was studied as an adjunct to antibiotics and physiotherapy in only 30 CAP patients; the small randomized trial is insufficient to establish it as definitive therapy. [70]A1b Lianhua Qingke tablets were studied for 7 days as adjunctive treatment in 160 children aged 4–14 years with mild Mycoplasma pneumoniae pneumonia; this limited population and disease-specific evidence does not justify routine use in severe CAP or as a substitute for effective antimicrobials. [145]A1b
Discharge, rehabilitation, and long-term surveillance
Discharge planning should include reassessment of oxygenation, functional capacity, nutrition, medication adherence, comorbidities, and the ability to obtain follow-up care; persistent or worsening symptoms require evaluation for treatment failure, resistant infection, complications, or an alternative diagnosis. Older adults may need assessment of social isolation because loneliness was associated with adverse long-term outcomes, including 180-day mortality and respiratory-infection readmission, in a multicenter cohort. [483]
CAP is associated with subsequent cardiovascular disease, including heart failure and acute coronary syndrome, and with deep-vein thrombosis and pulmonary embolism; post-discharge review should therefore address new chest pain, dyspnea, edema, palpitations, and thromboembolic symptoms, particularly in high-risk patients. [482] The international Long-term Pneumonia Mortality Index was derived and externally validated to estimate 1-year mortality after CAP hospitalization, providing a potential framework for identifying patients requiring intensified follow-up and preventive care. [12]B2b
Vitamin D deficiency at admission was associated with increased mortality in hospitalized adults with CAP, but this observational finding does not prove that supplementation improves survival; testing and replacement should follow established nutritional indications rather than be prescribed solely as CAP treatment. [484] Preventive care should include review of influenza vaccination, especially in adults aged ≥65 years, for whom adjuvanted and high-dose inactivated vaccines are preferentially recommended; a cluster-randomized crossover study directly compared their effectiveness against PCR-confirmed influenza. [302]A1b Prevention should also address smoking, aspiration risk, oral health, chronic disease control, and indicated pneumococcal and other vaccinations, with choices adapted to age, comorbidity, immune status, and local recommendations. [302]A1b
| Domain | Practical approach | Supporting evidence |
|---|---|---|
| Antibiotics | Narrow therapy when microbiology permits; use clinically appropriate oral step-down and avoid unnecessary extension | [133]B2b[464][472] |
| Steroids | Reserve for a defined indication or selected severe disease; do not extrapolate across populations | [95]A1b[480][481] |
| Thrombosis | Use standard risk-based thromboprophylaxis; do not automatically intensify dosing | [304]A1b |
| Follow-up | Assess function, social support, cardiovascular/thromboembolic symptoms, and longer-term mortality risk | [12]B2b[482][483] |
| Prevention | Review influenza and other indicated vaccines and modifiable risk factors | [302]A1b |
History and Evolution of Treatment
- ▸Recent CAP treatment research emphasizes oral step-down therapy, shorter antibiotic courses, and narrower empiric selection when clinically safe. [472] [133]
- ▸Antibiotic decisions are increasingly supported by interpreted CRP, procalcitonin, respiratory-virus testing, chest radiography, and individualized MDRO-risk estimates rather than by test results alone. [305] [306] [133]
- ▸Rapid pathogen-directed diagnosis is particularly important for Legionella and Chlamydia psittaci pneumonia, including use of targeted next-generation sequencing where conventional testing is limited. [461] [485] [267]
- ▸Adjunctive clarithromycin and pediatric dexamethasone have been evaluated in randomized trials, whereas traditional Chinese medicine, omega-3 fatty acids, and photobiomodulation remain population-specific or investigational adjuncts. [303] [480] [145] [477] [70]
- ▸Modern CAP management includes prevention, complication recognition, ICU-oriented supportive strategies, and post-discharge assessment of long-term mortality and cardiovascular risk. [302] [300] [304] [465] [12] [212]
From empiric therapy to precision antimicrobial selection
Treatment of community-acquired pneumonia (CAP) historically centered on prompt empiric antibacterial therapy, with subsequent adjustment according to microbiology, severity, host factors, and clinical response. Recent evidence increasingly supports shorter, narrower, and better-targeted treatment rather than routine prolonged broad-spectrum therapy. In hospitalized African children aged 2 months to 6 years with severe, uncomplicated CAP, the PediCAP factorial randomized trial directly evaluated intravenous-to-oral step-down treatment and the shortest effective total antibiotic duration, challenging the traditional WHO approach of 5 days of intravenous antibiotics. [472] The trial compared oral amoxicillin with amoxicillin-clavulanate after intravenous treatment and was designed to establish whether oral continuation and abbreviated courses were safe in children weighing 3–30 kg with point-of-care CRP >10 mg/L. [472]
Antimicrobial stewardship has also evolved from generic restriction policies to individualized decision support. In adults with cancer hospitalized for infection, the INSPIRE cluster-randomized trials evaluated computerized provider-order-entry prompts that supplied patient- and pathogen-specific multidrug-resistant-organism risk estimates to reduce unnecessary empiric extended-spectrum antibiotic use. [133]B2b In hospitalized adults with suspected respiratory infection, a pragmatic randomized trial tested electronic-health-record notes that translated low procalcitonin or a positive respiratory-virus test into an estimated post-test probability of bacterial pneumonia and linked that probability to antibiotic decisions; this approach addressed the limitation that testing alone often fails to change prescribing. [306]A1b
In outpatient care, treatment selection has increasingly incorporated objective confirmation. A randomized digital vignette study of French general practitioners compared usual clinical assessment with chest radiography, CRP testing, or both to determine whether these tools reduce antibiotic initiation in suspected CAP. [305]C4 Together, these studies represent a shift from treating every clinically suspected lower-respiratory infection toward treatment guided by estimated bacterial probability, while recognizing that a negative or low-bacterial-probability result must be interpreted in clinical context. [305]C4 [306]A1b
Pathogen-directed and immunomodulatory treatment
The modern treatment model retains empiric coverage for common bacterial pathogens but emphasizes rapid recognition of atypical and zoonotic causes. Legionella pneumonia requires effective Legionella-directed therapy, including a macrolide, fluoroquinolone, or doxycycline; a multicenter cohort specifically examined the relationship between delay to effective therapy and mortality, including the excess risk observed in immunocompromised patients. [461] Chlamydia psittaci remains an underdiagnosed zoonotic cause of CAP, and targeted next-generation sequencing of respiratory specimens, including sputum and bronchoalveolar lavage fluid, has been studied to shorten diagnostic delay and support antimicrobial stewardship, with empirical quinolone treatment examined as a therapeutic strategy. [485]C BALF combined with tNGS was also evaluated in a temporally associated series from resource-limited rural hospitals, where conventional diagnostic capacity was limited. [267]C4
Treatment evolution has included adjunctive anti-inflammatory therapy, although its role remains disease- and population-specific. In the ACCESS randomized trial, adding clarithromycin to standard care in hospitalized CAP was associated with earlier symptom resolution during the first 72 hours and prevention of progression to respiratory failure and secondary sepsis; molecular analyses investigated the pathways underlying these effects. [303]A1b A double-blind pediatric trial evaluated intravenous dexamethasone for 5 days in children aged 2 months to 15 years with severe CAP, assessing treatment failure at 72 hours, radiographic progression, respiratory failure, ventilation, shock, mortality, length of stay, readmission, and inflammatory markers. [480] Lianhua Qingke tablets were tested as a 7-day adjunct to conventional therapy in children aged 4–14 years with mild Mycoplasma pneumoniae pneumonia, in the context of increasing macrolide resistance. [145]A1b
Other adjuncts remain investigational. A pilot randomized study in enterally fed patients with severe pneumonia compared 3.50 g and 8.75 g/day of omega-3 fatty acids for 7 days with control treatment; supplementation was associated with shorter mechanical-ventilation duration and lower hospital costs, but the anticipated anti-inflammatory mechanism was not demonstrated. [477]C Photobiomodulation using a 940-nm infrared LED vest for 15 minutes daily over 7 days was evaluated in 30 adults alongside antibiotics and physiotherapy; the study assessed cardiopulmonary and hematologic outcomes rather than replacing conventional treatment. [70]A1b
Critical illness, COVID-19, and supportive treatment
For critically ill patients with COVID-19 pneumonia managed within the REMAP-CAP adaptive platform, ivermectin was compared with no ivermectin in critically and noncritically ill hospitalized patients, using respiratory- and cardiovascular-organ-support-free days through day 21 as the primary outcome. [300]A1b Intermediate-dose heparin was likewise compared with standard low-dose thromboprophylaxis in critically ill COVID-19 patients, with treatment continued for up to 14 days and organ-support-free days as the principal outcome. [304]A1b These studies illustrate how CAP treatment research expanded during the pandemic to include platform-trial evaluation of antiviral and thromboprophylactic strategies, while remaining distinct from routine treatment of non-COVID bacterial CAP. [300]A1b [304]A1b
Prevention, complications, and long-term care
Prevention has become part of the broader CAP treatment pathway. In adults aged ≥65 years, a cluster-randomized crossover study compared adjuvanted with high-dose inactivated influenza vaccines against PCR-confirmed influenza, addressing the uncertainty surrounding preferential vaccine selection in older adults. [302]A1b
Management has also broadened beyond the initial pulmonary infection. Pediatric pyopneumothorax caused by the anaerobe Prevotella oris highlighted the need to recognize unusual pathogens and complications, particularly after recent dental infection, and used metagenomic sequencing to support diagnosis and therapeutic planning. [465] CT-based severity scores have been studied in Chlamydia psittaci pneumonia to characterize disease burden and predict ICU admission, while creatine kinase and direct bilirubin were evaluated in a small retrospective cohort as a hypothesis-generating model for severe psittacosis; neither approach should be regarded as a validated replacement for established severity assessment. [278]B2b [210]B2b
Finally, CAP care is increasingly viewed as extending beyond discharge. The international Long-term Pneumonia Mortality Index was derived and externally validated to estimate 1-year mortality after CAP hospitalization, including validation in German, US, and COVID-19 pneumonia cohorts. [12]B2b A prospective cohort also evaluated Frank’s sign as a marker associated with cardiovascular events after pneumonia, reflecting recognition that survivors may require cardiovascular risk assessment and follow-up. [212]B2b
| Treatment direction | Evidence and clinical implication |
|---|---|
| Oral step-down and duration reduction | PediCAP directly tested oral amoxicillin or amoxicillin-clavulanate after intravenous therapy in children with severe uncomplicated CAP. [472] |
| Stewardship-guided empiric therapy | MDRO-risk prompts and probability-based interpretation of respiratory tests were evaluated to reduce unnecessary broad-spectrum antibiotic use. [133]B2b [306]A1b |
| Objective outpatient selection | CRP and chest radiography were tested as tools to reduce antibiotic initiation for suspected CAP. [305]C4 |
| Adjunctive therapy | Clarithromycin, dexamethasone, Lianhua Qingke, omega-3 fatty acids, and photobiomodulation were studied as additions to conventional care, with differing levels of evidence and applicability. [303]A1b [480] [145]A1b [477]C [70]A1b |
| Precision diagnosis | Legionella-directed treatment and tNGS-supported diagnosis of C. psittaci illustrate pathogen-specific management. [461] [485]C [267]C4 |
9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive)
- ▸The supplied evidence does not define universal oxygen, noninvasive-ventilation, or intubation thresholds; use local critical-care protocols and individualized assessment. [243][361][489]
- ▸For pediatric PPE or empyema requiring drainage, updated IDSA/PIDS guidance addresses chest-tube size and drainage with fibrinolysis versus surgical debridement. [358][359]
- ▸A living network meta-analysis found continuing uncertainty among antibiotics alone, chest tubes with or without fibrinolytics, video-assisted thoracoscopic surgery, and other modalities. [99]
- ▸Bronchoscopy is best reserved for selected severe, refractory, immunocompromised, diagnostically uncertain, or obstructive cases rather than routine uncomplicated CAP. [366][368][432][487][488][489][491]
- ▸Plastic bronchitis requires consideration when bronchoscopically visible casts obstruct the airways; one cohort identified 100 affected children among 761 undergoing bronchoscopy. [487]
- ▸Children with PPE or necrotizing pneumonia may develop long-term pulmonary sequelae, supporting spirometric and radiologic follow-up when clinically indicated. [486]
Scope and escalation
Respiratory support in community-acquired pneumonia (CAP) should be individualized to gas-exchange impairment, work of breathing, fatigue, and comorbidity, with escalation and monitoring in an appropriately staffed setting. The supplied evidence does not establish universal oxygen-saturation thresholds, preferred noninvasive modality, or intubation criteria; therefore, these decisions should follow local pediatric, adult, and critical-care protocols. [243]B2b[361]B2b[489]
The strongest procedure-specific evidence concerns complicated pediatric CAP, particularly parapneumonic effusion (PPE) and empyema. PPE and necrotizing pneumonia (NP) occur in approximately 3% of children with CAP in the cited pediatric cohort and may produce functional lung damage. [486] The 2026 IDSA/PIDS guideline update addresses thoracostomy-tube size and compares pleural drainage with fibrinolysis against surgical debridement using systematic reviews and GRADE methodology. [358]A1c[359]A1c
Pleural drainage and empyema
For children with pneumonia-associated pleural infection requiring drainage, the choice of chest-tube size should be guided by the updated IDSA/PIDS recommendation rather than by routine use of a large-bore tube; however, the supplied abstract does not report the guideline’s exact size threshold or strength of recommendation. [358]A1c Similarly, the guideline specifically evaluates chest-tube drainage with fibrinolysis versus mechanical surgical debridement, but the supplied abstract does not provide the final comparative recommendation or outcome estimates. [359]A1c
A living systematic review and network meta-analysis of randomized trials in patients younger than 18 years compared antibiotics alone, chest-tube insertion with or without fibrinolytics, video-assisted thoracoscopic surgery, and other conservative or surgical modalities for PPE or empyema. Its prespecified outcomes included hospital length of stay and other clinical outcomes, reflecting continuing uncertainty about the optimal initial intervention. [99]A1a Accordingly, procedural selection should incorporate disease organization, loculation, clinical trajectory, operator expertise, and availability of pediatric surgery and interventional radiology, while recognizing that the supplied references do not provide a universal algorithm. [99]A1a[358]A1c[359]A1c
Bronchoscopy and lower-airway sampling
Bronchoscopy is an adjunct for selected hospitalized or severe CAP—not a routine requirement for uncomplicated disease—when lower-airway sampling or therapeutic airway clearance is clinically indicated. This conclusion is supported by the cited studies being cohorts of children or adults who underwent bronchoscopy, often because routine treatment was ineffective or because severe disease required etiologic investigation; these observational designs do not establish that bronchoscopy improves outcomes for all CAP patients. [432][488][489][491]
In children, bronchoalveolar-lavage (BAL) testing has been used to characterize mixed infection, severe viral CAP with possible bacterial co-detection, and CMV DNA detection. [432][488][491] A multicenter pediatric study of 198 children indicated for fiberoptic bronchoscopy compared nasopharyngeal aspirates with BAL fluid using targeted next-generation sequencing and 16S rRNA sequencing; it reported high consistency for the first pathogen detected in upper- and lower-airway samples, while also examining differences in airway microbiota by pathogen and outcome groups. [366]B2b In adults with CAP, a prospective controlled comparison evaluated targeted next-generation sequencing in sputum versus BAL fluid because some patients cannot tolerate bronchoscopy or BAL cannot be obtained promptly. [368]B2b
Bronchoscopy may also be therapeutic when airway obstruction is present. In a retrospective bronchoscopy-based study of 761 children with CAP, 100 had plastic bronchitis with bronchoscopically observed casts; the study evaluated pathogen distribution, clinical characteristics, and risk factors for plastic bronchitis. [487]C A case report illustrates bedside fiberoptic bronchoscopy assisting diagnosis by sputum metagenomic sequencing in an adult with motor-neuron disease and Chlamydia psittaci pneumonia, but this represents very-low-level evidence and should not be generalized. [364]C4
High-risk hosts and procedure planning
Hospitalized solid-organ transplant recipients with CAP have been studied for ICU admission, in-hospital and 1-year mortality, cardiovascular events, diagnostic findings, and long-term outcomes, supporting a lower threshold for specialist assessment and respiratory monitoring in this population. [243]B2b A multicenter French cohort similarly characterized CAP in hospitalized kidney-transplant recipients, including ward and ICU admissions and diagnostic testing such as sputum culture. [361]B2b Patients with hematologic malignancy hospitalized for CAP were evaluated with bronchoscopy within 24 hours of admission to identify pathogens, underscoring the potential role of early lower-airway sampling in selected immunocompromised patients. [489]
Complications and follow-up
Complicated CAP may require coordinated respiratory, infectious-disease, interventional-pulmonology, radiology, and surgical care. [486] In the pediatric long-term-outcome study, follow-up included spirometry and radiologic assessment after PPE or NP, reflecting concern for persistent functional or structural sequelae. [486] Retrospective pediatric studies of Mycoplasma pneumoniae, Chlamydia pneumoniae, adenovirus, and group A streptococcus describe severe or complicated disease populations and may help identify patients who require hospitalization, intensive monitoring, bronchoscopy, or pleural intervention, but they do not by themselves define respiratory-support thresholds. [451][367]B2b[369]C4[363]B2b[490]
| Clinical situation | Procedure or evidence focus | Evidence limitation |
|---|---|---|
| Pediatric PPE or empyema requiring drainage | Chest-tube size; IDSA/PIDS 2026 update | Supplied abstract does not state the exact size recommendation. [358]A1c |
| Pediatric pleural infection | Chest-tube drainage with fibrinolysis versus mechanical debridement | Supplied abstract does not state the final comparative recommendation. [359]A1c |
| Loculated or persistent pediatric pleural infection | Antibiotics, chest tube with or without fibrinolytics, VATS, and other modalities | Living RCT network meta-analysis; optimal modality remains uncertain. [99]A1a |
| Severe, refractory, or diagnostically uncertain CAP | Bronchoscopy with BAL, targeted sequencing, or pathogen testing | Observational cohorts; no proof of universal outcome benefit. [366]B2b[432][488][489][491] |
| Suspected airway casts | Therapeutic bronchoscopy for plastic bronchitis | Retrospective bronchoscopy-based evidence. [487]C |
10. Complications
- ▸Respiratory failure and septic shock are more frequent in adults with T2DM and CAP; reported rates were 22.7% and 6.4%, respectively. [456]
- ▸In ACCESS, adjunctive clarithromycin was associated with symptom improvement within 72 hours and prevention of progression to respiratory failure and secondary sepsis. [303]
- ▸Empyema and pyopneumothorax are severe pediatric pleural complications; Prevotella oris is a rare reported anaerobic cause. [465]
- ▸Potential complications include pneumothorax, cardiovascular events, MIRM, plastic bronchitis, severe pathogen-specific pneumonia, shock, respiratory failure, and death. [84][212][222][376][456]
- ▸Most new risk estimates supplied here are observational; incomplete abstract data limit interpretation of several reported associations. [84][212][222][444][467][492][494][495][496][497]
Overview
Community-acquired pneumonia (CAP) may be complicated by pulmonary deterioration, pleural infection, air-leak syndromes, sepsis, cardiovascular events, extrapulmonary inflammatory disease, and death. Recent evidence is predominantly observational and should be interpreted as risk-association evidence rather than proof of causality. [303]A1b[212]B2b[456]
Respiratory failure and progression to severe disease
Respiratory failure is a major complication of CAP and may require non-invasive or invasive ventilatory support. In a retrospective cohort of 2,471 adults, respiratory failure occurred more frequently in patients with type 2 diabetes mellitus (T2DM) than in those without diabetes (22.7% vs 16.5%); septic shock was also more common (6.4% vs 3.5%), and mortality was higher (8.4% vs 4.3%). [456] Severe CAP with respiratory failure requiring ICU admission remains associated with substantial mortality, and a 164-patient ICU cohort developed a machine-learning model specifically to predict in-hospital death in this population. [468] A multicentre prospective study of 170 patients with severe CAP also compared ICU and non-ICU patients to identify mortality-associated characteristics, although the available evidence summary does not provide the complete mortality estimates or independent predictors. [495]
In the double-blind ACCESS randomised trial, adding clarithromycin to standard care in hospitalised CAP was reported to produce earlier symptom resolution during the first 72 hours and to prevent progression to respiratory failure and secondary sepsis. [303]A1b Transcriptomic, pathway, and cytokine analyses were undertaken to investigate these effects; the evidence supports a potential immunomodulatory mechanism but does not establish that clarithromycin should be used solely to prevent complications outside the trial context. [303]A1b
Pleural complications and pneumothorax
Parapneumonic effusion, empyema, and pyopneumothorax are important pulmonary complications, particularly in children. [465][496] A case report and literature review described pediatric pyopneumothorax caused by the anaerobic organism Prevotella oris after recent tooth extraction; bilateral pneumonia was present, and metagenomic next-generation sequencing helped establish the diagnosis. [465] This report highlights an uncommon anaerobic cause and the potential diagnostic value of molecular testing when routine evaluation is inconclusive, but it cannot estimate incidence or comparative treatment effectiveness. [465]
A retrospective TriNetX cohort study evaluated pneumothorax within 60 days after hospitalization for CAP in adults treated with fluoroquinolones versus non-fluoroquinolone antibiotics. [84]B2b Patients with connective-tissue disorders were excluded, and adjusted Cox regression was used to assess the association; the available abstract does not provide the hazard ratio or confirm whether fluoroquinolone exposure independently increased risk. [84]B2b Antibiotic class should therefore not be assumed to cause pneumothorax on the basis of this study alone. [84]B2b
Pediatric complicated pneumonia
A pediatric risk-stratification study classified hospitalized children as having uncomplicated CAP or complicated pneumonia and identified independent admission predictors using multivariable logistic regression. [496] The abstract indicates that older age was among the independent risk factors, but the available summary truncates the full list of predictors and their effect sizes. [496] In children with Mycoplasma pneumoniae pneumonia (MPP), a 3,081-patient cohort found that respiratory-pathogen co-detection was common (1,908 co-detection vs 1,173 monoinfection cases) and examined severe MPP, specific complications, healthcare use, and cost; the detailed complication frequencies are not available in the supplied evidence. [467]
Large pediatric surveillance studies further describe substantial pathogen-specific complication burdens. A 17,505-child retrospective study of MPP from 2018–2023 assessed adverse outcomes and associated factors, with the highest annual case count occurring in 2023 (4,619 cases). [451] Another cohort involving 175,350 children with acute respiratory infections evaluated age, season, macrolide resistance, and plastic bronchitis in relation to MPP risk. [376]B2b Severe MPP was also examined in 417 hospitalized children, including 210 severe and 207 general cases; admission clinical, laboratory, and imaging factors within the first 24 hours were assessed for early recognition of severe disease. [498]
Extrapulmonary and pathogen-specific complications
Mycoplasma pneumoniae can cause Mycoplasma pneumoniae-induced rash and mucositis (MIRM), an extrapulmonary syndrome characterized predominantly by mucosal involvement. [222]B2a A PRISMA systematic review of studies published from 2015–2025 evaluated the frequency of oral mucositis, diagnostic criteria, and outcomes in confirmed M. pneumoniae infection, supplemented by a case series; the supplied abstract does not provide pooled frequencies or outcome estimates. [222]B2a
Chlamydia pneumoniae pneumonia may likewise progress to severe disease and complications. A tertiary-hospital retrospective study enrolled 121 children diagnosed with C. pneumoniae pneumonia from 2022–2025 and compared severe with non-severe cases using the 2024 revised pediatric CAP criteria; detailed complication rates and independent risk factors are not included in the available summary. [497]C Adenovirus-associated respiratory infection was studied in hospitalized children in Shanghai from 2021–2023, integrating viral typing and normalized viral-load measurement to identify correlates of severe CAP; the abstract does not provide the specific severe-outcome estimates. [492] Staphylococcus aureus and respiratory-virus co-infection was investigated because of its potential synergistic pathogenic effect and poorer prognosis, with clinical and genomic analyses used to assess outcomes. [444]
Cardiovascular complications and mortality
Pneumonia may trigger cardiovascular complications, including new-onset atrial fibrillation or flutter and myocardial infarction. [212]B2b A prospective cohort of adults hospitalized with CAP assessed Frank’s sign, an acquired diagonal earlobe crease, at admission and followed patients for 18 months to examine a composite of cardiovascular endpoints. [212]B2b The study was single-center and observational; the supplied abstract does not provide the association estimate or event rate, so Frank’s sign should be regarded as a possible risk marker rather than a diagnostic test. [212]B2b
Mortality risk is amplified by severe respiratory failure, shock, comorbidity, and pathogen-related complications. [456][468][495] In children with severe CAP requiring ventilatory support within the first 2 days, a Japanese national-database propensity-score study evaluated corticosteroid exposure and in-hospital mortality, including subgroup analyses by cardiovascular status, organ failure, age, and microbial diagnosis; the available evidence does not provide a definitive treatment recommendation. [494]
Practical implications
Patients with CAP should be monitored for worsening oxygenation, increasing work of breathing, shock, altered mental status, pleural fluid or air leak, arrhythmia, myocardial ischemia, and extrapulmonary mucocutaneous disease. [303]A1b[212]B2b[222]B2a[456][465] Particular vigilance is warranted in patients with T2DM, severe MPP or pathogen co-detection, suspected S. aureus–viral co-infection, or early clinical and radiographic indicators of complicated pneumonia. [444][456][467][496][498]
| Complication or outcome | Evidence-supported context |
|---|---|
| Respiratory failure | More frequent with T2DM: 22.7% versus 16.5% without diabetes. [456] |
| Septic shock | More frequent with T2DM: 6.4% versus 3.5%. [456] |
| Pleural infection or pyopneumothorax | Severe pediatric complications; Prevotella oris was reported after recent tooth extraction. [465] |
| Pneumothorax | Studied within 60 days after hospitalization in adults treated with fluoroquinolone versus non-fluoroquinolone antibiotics; final association estimate unavailable. [84]B2b |
| Cardiovascular events | Prospective CAP cohort assessed atrial fibrillation/flutter and myocardial infarction over 18 months. [212]B2b |
| MIRM | Extrapulmonary M. pneumoniae complication with prominent mucositis. [222]B2a |
| Plastic bronchitis | Evaluated as a complication in a large pediatric M. pneumoniae cohort. [376]B2b |
| Mortality | Increased in adults with T2DM: 8.4% versus 4.3%; severe CAP with respiratory failure is a high-risk ICU population. [456][468] |
11. Prognosis and Natural History
- ▸CAP prognosis ranges from uncomplicated recovery to respiratory failure, shock, PARDS/ARDS, ICU admission, and death; risk assessment must be dynamic.[449][450]
- ▸T2DM was associated with higher septic shock, respiratory failure, and mortality rates in a 2,471-patient retrospective cohort.[456]
- ▸High-risk thresholds examined in the cited literature include PaCO₂ >45 mmHg, PaO₂/FiO₂ <300, corticosteroid doses of ≤400 mg hydrocortisone-equivalent/day, dexamethasone-equivalent doses ≥7.5 mg/day versus <7.5 mg/day, and antibiotic durations ≤5 days versus >5 days.[448][125][146][450][462]
- ▸Prediction scores, inflammatory biomarkers, and transcriptomic signatures may support risk stratification but do not replace repeated clinical assessment.[425][449][458]
- ▸The supplied references provide limited evidence on long-term post-discharge outcomes.[448][449][450]
Overall clinical course
Community-acquired pneumonia (CAP) has a heterogeneous course ranging from uncomplicated recovery to respiratory failure, septic shock, acute respiratory distress syndrome, intensive-care admission, and death. In the PROGRESS cohort, approximately one in five hospitalized patients was reported to require ICU admission, and delayed ICU admission was associated with increased risk; the study evaluated whether a five-gene blood transcriptomic signature could improve prediction of organ dysfunction and death beyond conventional clinical scores.[449] Prognosis therefore depends on early recognition of physiological deterioration, timely escalation of respiratory and circulatory support, and identification of high-risk host factors.[449]
The available 2026 evidence is predominantly short-term and hospital-based. It does not establish a single universal recovery trajectory or provide a definitive population-wide mortality estimate because the cited studies differ in age, disease severity, setting, geography, and design.[424][425][449][450][456][458]
Predictors of severe disease and death
In adults with CAP, type 2 diabetes mellitus (T2DM) was associated with more severe complications in a retrospective cohort of 2,471 patients: septic shock occurred in 6.4% versus 3.5% without diabetes, respiratory failure in 22.7% versus 16.5%, and mortality in 8.4% versus 4.3%, respectively.[456] These findings support diabetes as an adverse prognostic marker, although the observational design cannot prove that diabetes itself caused the excess risk.[456]
Among older adults admitted to the ICU, a prospective study of 227 patients compared SMART-COP, CURB-65, SOFA, and APACHE II for predicting ICU mortality, intubation, vasopressor requirement, and hospital-acquired pneumonia.[458] The study was specifically designed because commonly used severity scores were not developed or validated exclusively for older ICU patients; consequently, score performance should be interpreted in the context of age, comorbidity, and the need for organ support rather than as a substitute for repeated clinical assessment.[458]
In young children, admission inflammatory profiles may help identify those at risk for severe CAP and pediatric acute respiratory distress syndrome (PARDS). A prospective cohort of children aged under 5 years evaluated neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, systemic immune-inflammation index, systemic inflammation response index, C-reactive protein, and procalcitonin as routinely available prognostic biomarkers.[425] A separate pediatric study developed and internally validated a nomogram for severe CAP using 1,486 hospitalized children aged 0–? years; its population, etiological spectrum, and risk-factor model were derived from a single Chinese hospital and should not be assumed to generalize to other settings.[471]
Complications and special populations
Hypercapnia may identify particularly vulnerable patients with acute exacerbation of COPD complicated by severe pneumonia. In a retrospective dual-center cohort of 185 such patients, admission PaCO₂ was categorized as >45 mmHg, 35–45 mmHg, or <35 mmHg; the study examined ICU admission, short-term outcomes, inflammatory markers, and early anti-inflammatory responses.[462] The design supports risk stratification but does not establish that correcting hypercapnia changes prognosis.[462]
Legionella CAP is another high-risk phenotype in which treatment timing may influence outcome. A multicenter retrospective cohort of adults with laboratory-confirmed community-acquired Legionella pneumonia assessed time from presentation to effective therapy with a macrolide, fluoroquinolone, or doxycycline and examined mortality, including differences in immunocompromised patients.[461] These data emphasize the prognostic importance of prompt pathogen-directed treatment, while the observational design limits causal inference.[461]
CAP managed outside the ICU may nevertheless be physiologically severe. The Italian SIS-NET prospective cohort included 176 adults hospitalized outside the ICU with PaO₂/FiO₂ <300 and evaluated clinical characteristics, rapid molecular diagnostics, in-hospital mortality, and time to live discharge within 28 days.[450] Rapid molecular testing was assessed for its relationship with hospital outcomes, but the cited abstract does not establish a mortality benefit from testing itself.[450]
Treatment-related effects on prognosis
Antibiotic duration is relevant to recovery and antimicrobial stewardship. A 2026 meta-analysis of randomized trials in adults compared short-course therapy of ≤5 days with courses >5 days, using clinical success as the primary outcome and bacteriological and safety outcomes as secondary measures.[448] The evidence addresses whether shorter treatment preserves efficacy and safety; it should not be interpreted as support for abbreviated therapy in patients with persistent instability, complications, or inadequate clinical response.[448]
Adjunctive corticosteroid evidence concerns severe pulmonary infections, including CAP, sepsis, septic shock, and ARDS. A meta-analysis of randomized trials evaluated low-dose corticosteroids defined as ≤400 mg hydrocortisone-equivalent daily and assessed short-term mortality through 90 days, as well as 28- and 30-day mortality and adverse outcomes.[125]A1a A separate network meta-analysis of 32 randomized trials involving 9,746 participants compared dexamethasone-equivalent doses of ≥7.5 mg/day with lower doses of <7.5 mg/day for short-term mortality in hospitalized CAP.[146]A1a These analyses address dose and mortality, but treatment decisions remain dependent on disease severity, contraindications, and adverse-effect risk.[125]A1a[146]A1a
Pediatric and antimicrobial-treatment evidence
The PediCAP factorial randomized trial studied children aged 2 months to 6 years hospitalized with severe CAP without complicating factors in 13 hospitals across five sub-Saharan African countries. It assessed intravenous-to-oral step-down therapy with amoxicillin or amoxicillin-clavulanate and the shortest effective total antibiotic duration.[472] Its findings are most applicable to otherwise uncomplicated severe pediatric CAP in the studied settings, not automatically to adults, complicated pneumonia, or children with major comorbidity.[472]
Other cited studies provide treatment-specific rather than natural-history evidence. In elderly non-ICU inpatients, a retrospective IPTW-adjusted study compared omadacycline with tigecycline, moxifloxacin, and cefoperazone-sulbactam for clinical response, length of stay, microbiological clearance, and adverse events.[424] In children aged 8–16 years with macrolide-unresponsive Mycoplasma pneumoniae pneumonia, a small retrospective cohort compared intravenous omadacycline with continued azithromycin after persistent fever beyond 72 hours.[475]C A randomized trial in 160 children aged 4–14 years with mild Mycoplasma pneumoniae pneumonia assessed seven days of adjunctive Lianhua Qingke tablets versus placebo.[145]A1b These studies should not be used to infer long-term prognosis or superiority across all CAP populations.[424][475]C[145]A1b
Pathogen epidemiology may modify prognosis and management. A retrospective tNGS study included 838 children with CAP, while a separate pediatric cohort examined pathogen patterns from 2018–2023 and changes associated with pandemic-era non-pharmacological interventions.[452][459] A retrospective ICU cohort compared doxycycline- versus azithromycin-containing combination therapy for severe adult CAP, and a propensity-matched study compared hydrocortisone with methylprednisolone.[453][457] Finally, surveillance data on hospital-acquired pneumonia pathogens are not directly transferable to CAP natural history.[455]
Practical prognostic approach
Risk assessment should be dynamic: integrate age, comorbidity, oxygenation, ventilation, perfusion, inflammatory findings, pathogen-specific risks, and trajectory over serial examinations.[425][449][450][456][458][461][462] Worsening oxygenation, hypercapnia, shock, respiratory failure, or evolving organ dysfunction warrants urgent reassessment and consideration of ICU-level care.[449][450][462] Prognostic biomarkers, transcriptomic signatures, and prediction scores are adjuncts to—not replacements for—clinical judgment.[425][449][458]
Sources and limitations
The cited evidence includes randomized trials and meta-analyses, prospective cohorts, retrospective cohorts, and single-center studies. Observational associations may reflect residual confounding, and several studies are restricted to particular age groups, countries, hospitals, pathogens, or severity categories.[124]B3b[424][425][449][450][456][458][461][462] Long-term outcomes after hospital discharge, including persistent symptoms, functional decline, recurrent pneumonia, and late mortality, are not adequately characterized by the supplied references.[448][449][450]
| Domain | Evidence relevant to prognosis |
|---|---|
| Organ dysfunction | ICU admission, respiratory failure, shock, and death are central adverse outcomes.[449][456] |
| Oxygenation and ventilation | PaO₂/FiO₂ <300 and PaCO₂ >45 mmHg identify populations studied for severe disease and adverse outcomes.[450][462] |
| Host factors | T2DM and older age/ICU status are associated with higher-risk clinical contexts.[456][458] |
| Biomarkers and prediction tools | Inflammatory phenotypes, nomograms, SMART-COP, CURB-65, SOFA, APACHE II, and a five-gene signature were evaluated for risk prediction.[425][449][458][471] |
| Treatment factors | Shorter antibiotics, corticosteroid dose, and time to effective Legionella therapy were evaluated for mortality, success, or safety outcomes.[448][125]A1a[146]A1a[461] |
12. Special Populations & Pregnancy
- ▸The supplied references contain pediatric and geriatric evidence but no pregnancy-specific efficacy, safety, fetal-outcome, or pharmacokinetic data. [145,424,425,450,451,452,454,459,461,471,463,499,478,492,467,500,469,432]
- ▸In children aged <5 years, routinely available inflammatory biomarkers were evaluated for phenotyping and prediction of severe CAP and PARDS, but no universal biomarker cutoff is established by the supplied abstract. [425]
- ▸Macrolide-unresponsive pediatric MPP was studied after persistent fever >38.0°C following 72 hours of azithromycin; intravenous omadacycline evidence remains retrospective and limited to children aged 8–16 years. [475]
- ▸In older adults, functional walking ability and NLR may complement conventional severity assessment, while omadacycline evidence is observational. [424,478,500]
- ▸Immunocompromised patients with Legionella pneumonia require attention to timely effective therapy because treatment timing and mortality were specifically evaluated in this population. [461]
Scope of the available evidence
The supplied evidence is concentrated in children and older adults; it does not provide pregnancy-specific cohorts, pregnancy pharmacokinetic data, fetal outcomes, or recommendations for antibiotic selection during pregnancy. Accordingly, pregnancy management cannot be updated from these references alone and should be individualized using local obstetric and infectious-disease guidance. [145]A1b[424][425][450][451][452][454][459][461][471][463][499][478]C[492][467][500][469][432]
Infants and young children
Children hospitalized with CAP have heterogeneous etiologies and severity. A prospective cohort of children aged <5 years evaluated seven routinely available admission biomarkers—including C-reactive protein, procalcitonin, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, systemic immune-inflammation index, and systemic inflammation response index—to define inflammatory phenotypes and estimate the risk of severe CAP and pediatric acute respiratory distress syndrome (PARDS). The study supports biomarker-based risk stratification in settings where advanced cytokine frameworks are impractical, but the supplied abstract does not establish a universal cutoff or treatment algorithm. [425]
Large pediatric observational cohorts reinforce the importance of age-specific and pathogen-specific assessment. A 2018–2023 cohort included 17,505 hospitalized children aged 28 days to 14 years with Mycoplasma pneumoniae pneumonia (MPP), with the highest annual case count occurring in 2023; the study analyzed adverse outcomes and associated factors across the pandemic period. [451] A separate 2023–2024 cohort of 1,486 hospitalized children assessed etiologic patterns and predictors of severe CAP and developed an internally evaluated nomogram; Streptococcus pneumoniae and Haemophilus influenzae were among the leading detected bacterial pathogens. [471] In children with respiratory syncytial virus, adenovirus, or human metapneumovirus pneumonia, a 2025 cohort of 2,315 hospitalized children evaluated bacterial coinfection risk factors and inflammatory markers. [463]
Pediatric Mycoplasma pneumoniae pneumonia
Macrolide resistance and treatment failure are important considerations in pediatric MPP. In a randomized, double-blind, multicenter placebo-controlled trial, 160 children aged 4–14 years with mild MPP received conventional therapy plus Lianhua Qingke tablets or placebo for 7 days; the study was designed to assess adjunctive efficacy and safety, but the supplied abstract does not provide the outcome estimates. [145]A1b This evidence should not be extrapolated to severe disease, children outside the studied age range, or pregnancy.
For macrolide-unresponsive MPP, a retrospective cohort evaluated 64 hospitalized children aged 8–16 years who remained febrile at >38.0°C after 72 hours of azithromycin monotherapy. Eighteen received intravenous omadacycline using body-surface-area scaling from the approved adult regimen, while 46 continued azithromycin; outcomes included time to defervescence, 72-hour defervescence, radiologic improvement, corticosteroid use, and short-term safety. Because treatment allocation was nonrandomized and the sample was small, this study supports only cautious, specialist-directed consideration rather than routine pediatric use. [475]C
Coinfection may influence pediatric MPP severity and resource use. Among 3,081 children with confirmed MPP, 1,173 had monoinfection and 1,908 had respiratory-pathogen codetection; the study compared severe MPP, complications, healthcare utilization, and costs. [467] Molecular epidemiology and host-response studies likewise evaluated macrolide-resistance mutations, MLVA profiles, inflammatory markers, and risk factors for severe MPP in 421 hospitalized children. [454] Targeted next-generation sequencing was assessed in 838 children with CAP as a potential method for broader and more rapid pathogen detection, while another cohort used bronchoalveolar-lavage microbiology, inflammatory markers, and clinical variables to identify pediatric CAP phenotypes, including a mixed-infection phenotype. [452][432]
Pediatric diagnostics and uncommon complications
Respiratory pathogen detection remains clinically challenging because RSV and M. pneumoniae can produce overlapping presentations. A retrospective study developed and validated a blood-based machine-learning signature intended to distinguish hospitalized pediatric RSV infection from M. pneumoniae infection. [469] Multiplex PCR surveillance in children aged 0–18 years documented pneumococcal detection and bacterial codetection during 2022–2023, a period following pandemic-related changes in respiratory pathogen circulation. [499] Adenovirus studies in hospitalized children from 2021–2023 examined viral typing, normalized viral load, and correlates of severe CAP. [492]
Empyema and pyopneumothorax are severe pediatric complications. A case report described bilateral pneumonia with pyopneumothorax caused by the anaerobe Prevotella oris in a 10-year-old boy with a recent tooth extraction; metagenomic next-generation sequencing aided diagnosis. [465]
Older adults and functional vulnerability
In elderly non-ICU inpatients with CAP, a real-world retrospective study compared omadacycline with tigecycline, moxifloxacin, and cefoperazone–sulbactam after inverse-probability treatment weighting. Pragmatic clinical response required improvement in at least one laboratory, imaging, or symptom measure, with sensitivity analysis requiring improvement in all three; hospital stay, antibiotic duration, microbiological clearance, and adverse events were also assessed, including age subgroups <75 versus ≥75 years. [424] These observational data do not establish superiority or replace individualized assessment of renal, hepatic, gastrointestinal, and drug-interaction risks.
Functional status may add prognostic information beyond conventional scores. A multicenter study of patients aged ≥65 years evaluated premorbid walking ability as a predictor of 28-day mortality, excluding conditions that independently impaired walking. [500] Another study assessed whether adding the neutrophil-to-lymphocyte ratio to CURB-65 improved identification of high-risk elderly patients, including separate age strata of 65–79 years and ≥80 years. [478]C
Immunocompromised adults and severe disease
Among adults hospitalized with laboratory-confirmed community-acquired Legionella pneumonia, a multicenter cohort evaluated the association between time to effective Legionella-directed therapy and mortality and examined whether delayed therapy contributed to excess mortality among immunocompromised patients. Effective therapy included a macrolide, fluoroquinolone, or doxycycline. [461] In a separate multicenter Italian cohort of 176 adults managed outside the ICU, all participants had a PaO₂/FiO₂ ratio <300; the study characterized clinical, radiologic, microbiologic, therapeutic, and outcome features and assessed the effect of rapid molecular diagnostics on hospital outcomes. [450]
| Population or clinical issue | Evidence and applicability |
|---|---|
| Children <5 years | Admission inflammatory biomarkers were studied for severe CAP and PARDS risk stratification; no universal cutoff supplied. [425] |
| Children aged 4–14 years with mild MPP | Randomized trial of 7-day adjunctive Lianhua Qingke tablets; outcome estimates are not provided in the supplied abstract. [145]A1b |
| Children aged 8–16 years with macrolide-unresponsive MPP | Retrospective comparison of intravenous omadacycline versus continued azithromycin after persistent fever >38.0°C at 72 hours. [475]C |
| Older adults | Omadacycline was compared with three alternative regimens in a weighted real-world cohort; outcomes included response and adverse events. [424] |
| Adults aged ≥65 years | Walking ability and NLR combined with CURB-65 were evaluated for mortality-risk assessment. [478]C[500] |
| Immunocompromised adults with Legionella CAP | Time to effective Legionella-directed therapy and mortality were evaluated. [461] |
| Pregnancy | No pregnancy-specific evidence was included in the supplied references. [145]A1b[424][425][450][451][452][454][459][461][471][463][499][478]C[492][467][500][469][432] |
13. Prevention, Screening & Surveillance
- ▸Use age, CKD, HIV-related immune status, cancer, vaccination history, and time since vaccination to identify prevention priorities. [302,415,416,417,503,505]
- ▸Do not assume that adjuvanted influenza vaccine is superior to high-dose vaccine based on the supplied randomized-study abstract; comparative outcomes were not provided. [302]
- ▸Maintain local, age-specific, and post-pandemic pathogen and antimicrobial-resistance surveillance. [156,418,459,507,509]
- ▸Use diagnostic-stewardship metrics for pneumococcal urinary-antigen testing, including indication and positivity rate. [510]
- ▸Track CAP outcomes beyond discharge, including 30-day readmission, recurrent disease, adverse outcomes, and costs. [502,506]
Vaccination as primary prevention
Vaccination remains the principal preventive strategy relevant to pneumococcal and influenza-associated community-acquired pneumonia (CAP), particularly in older adults and people with chronic disease. Adults aged ≥65 years in the United States are preferentially offered either an adjuvanted or high-dose inactivated influenza vaccine annually; a 2023–2024 pragmatic cluster-randomized crossover study at 65 Kaiser Permanente Northern California facilities was designed to compare their relative effectiveness against polymerase chain reaction-confirmed influenza, addressing the previous lack of direct randomized comparison. [302]A1b Because the supplied evidence summary does not report the comparative outcome, it should not be used to claim superiority of either formulation. [302]A1b
A systematic review and meta-analysis evaluated vaccine efficacy in patients with stage 1–5 non-dialysis chronic kidney disease (CKD-ND), a population with increased infection risk and higher hospitalization and mortality risk. [415]B2a The review included randomized and observational studies identified through April 2025 and assessed both immunologic outcomes, including seroconversion and antibody titres, and clinical outcomes. [415]B2a CKD status should therefore be incorporated into vaccination assessment and surveillance, while acknowledging that vaccine response and clinical protection may vary by CKD stage and study design. [415]B2a
Pneumococcal vaccination is particularly relevant in older adults. A retrospective causal-forest analysis examined whether the association between pneumococcal vaccination and severe CAP was uniform among hospitalized patients aged ≥65 years; the study estimated an overall association using multivariable logistic regression and explored subgroup heterogeneity. [503] A multicenter matched case-control study in eastern China assessed 23-valent pneumococcal polysaccharide vaccine (PPV23) effectiveness against CAP hospitalization among adults aged ≥60 years, including protection over periods extending beyond 5 years after vaccination in a low-coverage setting. [505] These studies support evaluating both vaccination status and time since vaccination when interpreting severe CAP risk, but their observational designs do not establish a universal causal effect or a single duration of protection. [503][505]
Indirect protection may also be important. An analysis of Portuguese national hospitalizations evaluated adult CAP trends from 2000–2019 and the effect of universal, free pediatric pneumococcal vaccination introduced in January 2015 with 13-valent pneumococcal conjugate vaccine. [504] Pediatric pneumococcal immunization should therefore be considered when interpreting population-level adult CAP surveillance, although ecological and retrospective analyses cannot isolate vaccination effects from other temporal changes. [504]
People with HIV remain a high-priority prevention population. A nationwide cohort of adults with HIV in care from 2010–2023 assessed CAP incidence according to age, CD4 count, and duration of antiretroviral therapy (ART), specifically to inform more individualized vaccination strategies. [417]B2b Preventive review should therefore integrate age, CD4 count, and ART duration, rather than relying on any single characteristic alone. [417]B2b
Pathogen and antimicrobial-resistance surveillance
Local surveillance is essential because pathogen distributions and resistance patterns vary geographically and over time. A systematic review and meta-analysis synthesized microbial etiology and antimicrobial resistance among hospitalized pneumonia patients in Kazakhstan. [418]C4 A retrospective Indonesian tertiary-hospital cohort evaluated bacterial pathogens, resistance patterns, and clinical outcomes among adults hospitalized with pneumonia during 2024. [156]B2b These data support maintaining institution- and region-specific surveillance rather than assuming that pathogen prevalence or resistance findings from another country apply locally. [418]C4[156]B2b
Respiratory pathogen patterns changed during and after COVID-19-related non-pharmaceutical interventions (NPIs). In hospitalized children with CAP in Changzhou, China, pathogen characteristics were compared across 2018–2023, including bacterial and viral targets. [459] A Fujian inpatient analysis covering 2017–2024 found pathogen positivity of 82.73% overall, with positivity differing across pre-pandemic, mid-pandemic, and post-pandemic periods: 88.22%, 68.90%, and 83.71%, respectively. [509] In Shanghai children hospitalized with acute respiratory tract infections from 2021–2023, adenovirus typing, normalized viral-load measurement, and clinical outcomes were integrated to examine associations with severe CAP. [492] These findings support continued age-specific, season-specific, and post-NPI surveillance rather than extrapolation from pre-pandemic pathogen patterns. [459][492][509]
The 2023 resurgence of Mycoplasma pneumoniae in Chinese children was investigated using genomic epidemiology, including 685 isolates and historical and global sequence data; the study specifically evaluated macrolide resistance and evolutionary dynamics. [507] Resurgence surveillance should therefore include resistance testing and, where available, genomic characterization, especially when clinical activity increases after a period of low detection. [507]
Surveillance should distinguish community-acquired disease from healthcare-associated syndromes. A 61-hospital Suzhou study compared pathogens in ventilator-associated pneumonia and non-ventilator-associated hospital-acquired pneumonia from 2020–2024, demonstrating the value of separating these cohorts in infection-prevention surveillance. [455]
Diagnostic and outcome surveillance
Legionella surveillance can be strengthened by molecular testing. A multicenter cohort evaluated a fluorescence-resonance-energy-transfer real-time PCR assay targeting the Legionella 5S rRNA gene; melting-temperature analysis was used to discriminate species and assess associations with disease severity among laboratory-confirmed infections from 2019–2025. [501]
Pneumococcal urinary-antigen testing requires diagnostic stewardship. In a decade-long tertiary-hospital review, 7,178 tests performed from 2014–2023 had a 7.6% positivity rate; 42% were ordered in patients without a CAP diagnosis, generating approximately €17,000 annually in avoidable testing. [510] Testing surveillance should therefore monitor indication, positivity, downstream antimicrobial decisions, and whether positive results trigger vaccination recommendations. [510]
Cancer patients with pneumococcal CAP have higher mortality than the general population. In a prospective study of 912 adults with cancer and CAP, 94.6% were hospitalized, and pneumococcal serotypes were investigated using a PCV15 serotype-specific urinary-antigen assay with culture and blood or respiratory microbiology correlation. [416]B2b Cancer status and immunosuppression should be captured in prevention and outcome registries. [416]B2b
CAP surveillance should extend beyond discharge. A Finnish nationwide registry study followed adults with invasive pneumococcal disease, inpatient CAP, and outpatient CAP with matched controls to assess adverse outcomes and costs beyond direct treatment; 40–60% had at least one predefined medical risk factor, while a substantial proportion had none. [502] A prospective Ethiopian study followed 177 survivors of severe CAP after discharge to assess 30-day all-cause readmission and associated determinants. [506] Post-discharge surveillance should therefore include readmission, recurrent illness, comorbidity, vaccination status, and longer-term outcomes, not only acute mortality. [502][506]
Prevention surveillance priorities
A practical CAP prevention registry should record age, CKD, HIV-related immune status, cancer, pneumococcal and influenza vaccination, time since vaccination, pathogen testing, antimicrobial susceptibility, hospitalization, readmission, and death. [302]A1b[415]B2a[416]B2b[417]B2b[503][505][506] Analyses should be stratified by geography, age, pediatric versus adult population, pandemic phase, and community- versus healthcare-acquired classification because these factors materially influence observed pathogen patterns and prevention effects. [455][459][504][509]
Key limitations
Most evidence supplied for pneumococcal vaccination, pathogen distribution, diagnostic utilization, and outcomes is observational, retrospective, ecological, or single-region; residual confounding, selection bias, and limited generalizability must be considered. [156]B2b[416]B2b[417]B2b[418]C4[455][459][492][501][502][503][504][505][506][509][510] The influenza comparison is randomized and pragmatic, but the provided abstract does not include its effect estimates. [302]A1b The CKD evidence combines randomized and observational studies and includes immunologic as well as clinical endpoints, so laboratory response should not automatically be equated with prevention of CAP hospitalization. [415]B2a
| Domain | Variables or thresholds to monitor | Supporting evidence |
|---|---|---|
| Influenza vaccination | Adults ≥65 years; adjuvanted versus high-dose formulation; annual season | [302]A1b |
| Pneumococcal vaccination | Adults ≥60 years or ≥65 years in the cited studies; vaccine type; time since vaccination; severe CAP | [503][505] |
| Immunocompromising conditions | CKD stage 1–5, HIV, CD4 count, ART duration, cancer | [415]B2a[416]B2b[417]B2b |
| Diagnostics | Pneumococcal urinary-antigen test indication and positivity; Legionella PCR species discrimination | [501][510] |
| Epidemiology | Pediatric and adult pathogen trends; pre-, mid-, and post-pandemic periods; geographic variation | [418]C4[459][492][504][509] |
| Outcomes | Hospitalization, mortality, 30-day readmission, longer-term adverse outcomes, and costs | [502][506] |
References
- [1]
Jones BE, Ramirez JA, Oren E et al.. “Diagnosis and Management of Community-acquired Pneumonia: An Official American Thoracic Society Clinical Practice Guideline.” American journal of respiratory and critical care medicine (2026). PMID: 40679934 ↗
L1GUIDELINECited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), History and Evolution of Treatment - [2]
Metlay JP, Waterer GW, Long AC et al.. “Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America.” American journal of respiratory and critical care medicine (2019). PMID: 31573350 ↗
L1GUIDELINECited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), History and Evolution of Treatment - [3]
Evans SE, Jennerich AL, Azar MM et al.. “Nucleic Acid-based Testing for Noninfluenza Viral Pathogens in Adults with Suspected Community-acquired Pneumonia. An Official American Thoracic Society Clinical Practice Guideline.” American journal of respiratory and critical care medicine (2021). PMID: 33929301 ↗
L1GUIDELINECited in: 1. Definition, Classification and Nomenclature, History and Evolution of Treatment, 11. Prognosis and Natural History - [4]
Claessens YE, Debray MP, Tubach F et al.. “Early Chest Computed Tomography Scan to Assist Diagnosis and Guide Treatment Decision for Suspected Community-acquired Pneumonia.” American journal of respiratory and critical care medicine (2015). PMID: 26168322 ↗
L2TRIAL_NONRANDOMCited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, History and Evolution of Treatment - [5]
Michels EHA, Dequin PF, Butler JM et al.. “Quantifying immune dysregulation in pneumonia and sepsis with a parsimonious machine-learning model: a multicohort analysis across care settings and reanalysis of a hydrocortisone randomised controlled trial.” The Lancet. Respiratory medicine (2026). PMID: 41856148 ↗
L2RCTCited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [6]
Harris M, Clark J, Coote N et al.. “British Thoracic Society guidelines for the management of community acquired pneumonia in children: update 2011.” Thorax (2011). PMID: 21903691 ↗
L1GUIDELINECited in: 1. Definition, Classification and Nomenclature, History and Evolution of Treatment - [7]
Thomson A, Harris M. “Community-acquired pneumonia in children: what's new?” Thorax (2011). PMID: 21933948 ↗
L5GUIDELINECited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, History and Evolution of Treatment - [8]
Davenport EE, Burnham KL, Radhakrishnan J et al.. “Genomic landscape of the individual host response and outcomes in sepsis: a prospective cohort study.” The Lancet. Respiratory medicine (2016). PMID: 26917434 ↗
L2COHORTCited in: 1. Definition, Classification and Nomenclature, 2. Pathophysiology and Mechanism, 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [9]
Scicluna BP, van Vught LA, Zwinderman AH et al.. “Classification of patients with sepsis according to blood genomic endotype: a prospective cohort study.” The Lancet. Respiratory medicine (2017). PMID: 28864056 ↗
L2COHORTCited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [10]
Vestjens SMT, Spoorenberg SMC, Rijkers GT et al.. “High-sensitivity cardiac troponin T predicts mortality after hospitalization for community-acquired pneumonia.” Respirology (Carlton, Vic.) (2017). PMID: 28221010 ↗
L2RCTCited in: 1. Definition, Classification and Nomenclature, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [11]
Wunderink RG, Walley KR. “Update in sepsis and pulmonary infections 2013.” American journal of respiratory and critical care medicine (2014). PMID: 24983219 ↗
L5OTHERCited in: 1. Definition, Classification and Nomenclature, 6. Severity, Staging and Risk Stratification - [12]
Méndez R, González-Jiménez P, Latorre A et al.. “The Long-term Pneumonia Mortality Index: an international multicenter derivation and validation study for patients with community-acquired pneumonia.” American journal of respiratory and critical care medicine (2026). PMID: 41738235 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 8. Long-term and Definitive Management, 11. Prognosis and Natural History - [13]
Bedi P, Davidson DJ, McHugh BJ et al.. “Blood Neutrophils Are Reprogrammed in Bronchiectasis.” American journal of respiratory and critical care medicine (2018). PMID: 29733693 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature, 2. Pathophysiology and Mechanism, 7. Acute Management and Exacerbation Rescue - [14]
Ranzani OT, Prina E, Menéndez R et al.. “New Sepsis Definition (Sepsis-3) and Community-acquired Pneumonia Mortality. A Validation and Clinical Decision-Making Study.” American journal of respiratory and critical care medicine (2017). PMID: 28613918 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature, 7. Acute Management and Exacerbation Rescue - [15]
Komiya K, Ishii H, Umeki K et al.. “Impact of aspiration pneumonia in patients with community-acquired pneumonia and healthcare-associated pneumonia: a multicenter retrospective cohort study.” Respirology (Carlton, Vic.) (2013). PMID: 23231701 ↗
L2COHORTCited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [16]
Cilloniz C, Ferrer M, Liapikou A et al.. “Acute respiratory distress syndrome in mechanically ventilated patients with community-acquired pneumonia.” The European respiratory journal (2018). PMID: 29545274 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature, 7. Acute Management and Exacerbation Rescue - [17]
Gutierrez P, Closa D, Piñer R et al.. “Macrophage activation in exacerbated COPD with and without community-acquired pneumonia.” The European respiratory journal (2009). PMID: 20032016 ↗
L5OTHERCited in: 1. Definition, Classification and Nomenclature, 7. Acute Management and Exacerbation Rescue - [18]
Kolditz M, Ewig S, Höffken G. “Management-based risk prediction in community-acquired pneumonia by scores and biomarkers.” The European respiratory journal (2012). PMID: 23018905 ↗
L5REVIEW_NARRATIVECited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 10. Complications, 11. Prognosis and Natural History - [19]
Ginsburg AS, Klugman KP. “Antibiotics for paediatric community-acquired pneumonia in resource-constrained settings.” The European respiratory journal (2020). PMID: 32943429 ↗
L5OTHERCited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 13. Prevention, Screening & Surveillance - [20]
Long B, Gottlieb M. “2025 guideline updates for community-acquired pneumonia diagnosis and management.” The American journal of emergency medicine (2026). PMID: 42127879 ↗
L5GUIDELINECited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, History and Evolution of Treatment - [21]
Backman K, Helminen M, Kekäläinen E et al.. “Working group summary of the 2023 full update of the Finnish national guidelines for paediatric lower respiratory tract infections.” Acta paediatrica (Oslo, Norway : 1992) (2024). PMID: 39487609 ↗
L1GUIDELINECited in: 1. Definition, Classification and Nomenclature - [22]
Restrepo MI, Mortensen EM, Velez JA et al.. “A comparative study of community-acquired pneumonia patients admitted to the ward and the ICU.” Chest (2007). PMID: 17989157 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [23]
Dean NC, Bateman KA, Donnelly SM et al.. “Improved clinical outcomes with utilization of a community-acquired pneumonia guideline.” Chest (2006). PMID: 16963677 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature - [24]
Kyriacou DN, Yarnold PR, Stein AC et al.. “Discriminating inhalational anthrax from community-acquired pneumonia using chest radiograph findings and a clinical algorithm.” Chest (2007). PMID: 17296652 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature - [25]
Restrepo MI, Mortensen EM, Rello J et al.. “Late admission to the ICU in patients with community-acquired pneumonia is associated with higher mortality.” Chest (2009). PMID: 19880910 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature - [26]
Akram AR, Singanayagam A, Choudhury G et al.. “Incidence and prognostic implications of acute kidney injury on admission in patients with community-acquired pneumonia.” Chest (2010). PMID: 20435657 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature - [27]
Renaud B, Schuetz P, Claessens YE et al.. “Proadrenomedullin improves Risk of Early Admission to ICU score for predicting early severe community-acquired pneumonia.” Chest (2012). PMID: 22661450 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature - [28]
Pervaiz F, Chavez MA, Ellington LE et al.. “Building a Prediction Model for Radiographically Confirmed Pneumonia in Peruvian Children: From Symptoms to Imaging.” Chest (2018). PMID: 30291926 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature - [29]
Sun HK, Nicolau DP, Kuti JL. “Resource utilization of adults admitted to a large urban hospital with community-acquired pneumonia caused by Streptococcus pneumoniae.” Chest (2006). PMID: 16963679 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature - [30]
Principi N, Esposito S. “Management of severe community-acquired pneumonia of children in developing and developed countries.” Thorax (2010). PMID: 20965930 ↗
L5REVIEW_NARRATIVECited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 10. Complications, 11. Prognosis and Natural History - [31]
Brown JS, Lipman MC, Zar HJ. “What's new in respiratory infections and tuberculosis 2008-2010.” Thorax (2011). PMID: 21502098 ↗
L5REVIEW_NARRATIVECited in: 1. Definition, Classification and Nomenclature, 13. Prevention, Screening & Surveillance - [32]
Daniel P, Bewick T, Welham S et al.. “Adults miscoded and misdiagnosed as having pneumonia: results from the British Thoracic Society pneumonia audit.” Thorax (2017). PMID: 28108620 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature, 4. Clinical Presentation - [33]
Fally M, Hansel J, Robey RC et al.. “Decoding community-acquired pneumonia: a systematic review and analysis of diagnostic criteria and definitions used in clinical trials.” Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases (2024). PMID: 39725075 ↗
L1TRIAL_NONRANDOMCited in: 1. Definition, Classification and Nomenclature - [34]
Almirall J, Boixeda R, de la Torre MC et al.. “Factors driving outcome variability in aspiration and community-acquired pneumonia: a meta-analysis.” European respiratory review : an official journal of the European Respiratory Society (2025). PMID: 41062168 ↗
L2SR_OBSCited in: 1. Definition, Classification and Nomenclature - [35]
Dinh A, Barbier F, Bedos JP et al.. “Update of guidelines for management of Community Acquired pneumonia in adults by the French Infectious Disease Society (SPILF) and the French-Speaking Society of Respiratory Diseases (SPLF): Endorsed by the French intensive care society (SRLF), the French microbiology society (SFM), the French radiology society (SFR) and the French emergency society (SFMU).” Respiratory medicine and research (2025). PMID: 40037948 ↗
L1GUIDELINECited in: 1. Definition, Classification and Nomenclature - [36]
Stern A, Skalsky K, Avni T et al.. “Corticosteroids for pneumonia.” The Cochrane database of systematic reviews (2017). PMID: 29236286 ↗
L1SR_OBSCited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 10. Complications, 11. Prognosis and Natural History - [37]
Pakhale S, Mulpuru S, Verheij TJ et al.. “Antibiotics for community-acquired pneumonia in adult outpatients.” The Cochrane database of systematic reviews (2014). PMID: 25300166 ↗
L1SR_OBSCited in: 1. Definition, Classification and Nomenclature, 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [38]
Bjerre LM, Verheij TJ, Kochen MM. “Antibiotics for community acquired pneumonia in adult outpatients.” The Cochrane database of systematic reviews (2009). PMID: 19821292 ↗
L1SR_OBSCited in: 1. Definition, Classification and Nomenclature, 12. Special Populations & Pregnancy - [39]
Das RR, Singh M, Naik SS. “Vitamin D as an adjunct to antibiotics for the treatment of acute childhood pneumonia.” The Cochrane database of systematic reviews (2023). PMID: 36633175 ↗
L1SR_OBSCited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [40]
Chen S, Jiang Y, Lv D et al.. “Identification of subtypes and construction of a predictive model for novel subtypes in severe community-acquired pneumonia based on clinical metagenomics: a multicenter, retrospective cohort study.” Frontiers in cellular and infection microbiology (2025). PMID: 41446276 ↗
L3COHORTCited in: 1. Definition, Classification and Nomenclature - [41]
Dobler CC, Waterer G. “Healthcare-associated pneumonia: a US disease or relevant to the Asia Pacific, too?” Respirology (Carlton, Vic.) (2013). PMID: 23714303 ↗
L5REVIEW_NARRATIVECited in: 1. Definition, Classification and Nomenclature, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [42]
Ishida T, Miyashita N, Nakahama C. “Clinical differentiation of atypical pneumonia using Japanese guidelines.” Respirology (Carlton, Vic.) (2007). PMID: 17207034 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature, 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 12. Special Populations & Pregnancy - [43]
Kelly E, MacRedmond RE, Cullen G et al.. “Community-acquired pneumonia in older patients: does age influence systemic cytokine levels in community-acquired pneumonia?” Respirology (Carlton, Vic.) (2009). PMID: 19272082 ↗
L2OTHERCited in: 1. Definition, Classification and Nomenclature, 7. Acute Management and Exacerbation Rescue, 12. Special Populations & Pregnancy - [44]
Taylor SP, Taylor BT. “Health care-associated pneumonia in haemodialysis patients: clinical outcomes in patients treated with narrow versus broad spectrum antibiotic therapy.” Respirology (Carlton, Vic.) (2013). PMID: 23066809 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature - [45]
Henry C, Boethel C, Copeland LA et al.. “Clinical Utility of Testing for Legionella Pneumonia in Central Texas.” Annals of the American Thoracic Society (2017). PMID: 27739904 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature, History and Evolution of Treatment - [46]
McCauley LM, Webb BJ, Sorensen J et al.. “Use of Tracheal Aspirate Culture in Newly Intubated Patients with Community-Onset Pneumonia.” Annals of the American Thoracic Society (2016). PMID: 26793950 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue - [47]
Vaidyanathan A, Guiot J, Zerka F et al.. “An externally validated fully automated deep learning algorithm to classify COVID-19 and other pneumonias on chest computed tomography.” ERJ open research (2022). PMID: 35509437 ↗
L3OTHERCited in: 1. Definition, Classification and Nomenclature, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [48]
Giamarellos-Bourboulis EJ, Siampanos A, Bolanou A et al.. “Clarithromycin for early anti-inflammatory responses in community-acquired pneumonia in Greece (ACCESS): a randomised, double-blind, placebo-controlled trial.” The Lancet. Respiratory medicine (2024). PMID: 38184008 ↗
L1RCTCited in: 2. Pathophysiology and Mechanism, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [49]
Brown AO, Millett ER, Quint JK et al.. “Cardiotoxicity during invasive pneumococcal disease.” American journal of respiratory and critical care medicine (2015). PMID: 25629643 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism, 3. Epidemiology, Etiology and Risk Factors - [50]
Michels EHA, Peters-Sengers H, de Brabander J et al.. “The Plasma Proteome in Community-acquired Pneumonia: Pathophysiology, Outcome, and 10-Year Risk.” American journal of respiratory and critical care medicine (2025). PMID: 40600965 ↗
L3OTHERCited in: 2. Pathophysiology and Mechanism, 8. Long-term and Definitive Management, 11. Prognosis and Natural History - [51]
Waterer GW, Rello J, Wunderink RG. “Management of community-acquired pneumonia in adults.” American journal of respiratory and critical care medicine (2010). PMID: 20693379 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism, 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 8. Long-term and Definitive Management, 11. Prognosis and Natural History - [52]
Reyes LF, Restrepo MI, Hinojosa CA et al.. “Severe Pneumococcal Pneumonia Causes Acute Cardiac Toxicity and Subsequent Cardiac Remodeling.” American journal of respiratory and critical care medicine (2017). PMID: 28614669 ↗
L4OTHERCited in: 2. Pathophysiology and Mechanism, 10. Complications - [53]
Burnham KL, Davenport EE, Radhakrishnan J et al.. “Shared and Distinct Aspects of the Sepsis Transcriptomic Response to Fecal Peritonitis and Pneumonia.” American journal of respiratory and critical care medicine (2017). PMID: 28036233 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism, 4. Clinical Presentation - [54]
Preston JA, Bewley MA, Marriott HM et al.. “Alveolar Macrophage Apoptosis-associated Bacterial Killing Helps Prevent Murine Pneumonia.” American journal of respiratory and critical care medicine (2019). PMID: 30649895 ↗
L5OTHERCited in: 2. Pathophysiology and Mechanism, 7. Acute Management and Exacerbation Rescue - [55]
van Vught LA, Scicluna BP, Wiewel MA et al.. “Comparative Analysis of the Host Response to Community-acquired and Hospital-acquired Pneumonia in Critically Ill Patients.” American journal of respiratory and critical care medicine (2016). PMID: 27267747 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism - [56]
Park SY, Shrestha S, Youn YJ et al.. “Autophagy Primes Neutrophils for Neutrophil Extracellular Trap Formation during Sepsis.” American journal of respiratory and critical care medicine (2017). PMID: 28358992 ↗
L4OTHERCited in: 2. Pathophysiology and Mechanism - [57]
Marriott HM, Jackson LE, Wilkinson TS et al.. “Reactive oxygen species regulate neutrophil recruitment and survival in pneumococcal pneumonia.” American journal of respiratory and critical care medicine (2008). PMID: 18202350 ↗
L5OTHERCited in: 2. Pathophysiology and Mechanism, 7. Acute Management and Exacerbation Rescue - [58]
Singanayagam A, Singanayagam A, Elder DH et al.. “Is community-acquired pneumonia an independent risk factor for cardiovascular disease?” The European respiratory journal (2011). PMID: 21737556 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism, 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, 11. Prognosis and Natural History - [59]
Defres S, Marwick C, Nathwani D. “MRSA as a cause of lung infection including airway infection, community-acquired pneumonia and hospital-acquired pneumonia.” The European respiratory journal (2009). PMID: 19948913 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism - [60]
Almirall J, Rofes L, Serra-Prat M et al.. “Oropharyngeal dysphagia is a risk factor for community-acquired pneumonia in the elderly.” The European respiratory journal (2012). PMID: 22835620 ↗
L3OTHERCited in: 2. Pathophysiology and Mechanism, 12. Special Populations & Pregnancy - [61]
Fatykhova D, Fritsch VN, Siebert K et al.. “Microenvironmental acidification by pneumococcal sugar consumption fosters barrier disruption and immune suppression in the human alveolus.” The European respiratory journal (2024). PMID: 39231629 ↗
L5OTHERCited in: 2. Pathophysiology and Mechanism - [62]
Bordon J, Wiemken T, Peyrani P et al.. “Decrease in long-term survival for hospitalized patients with community-acquired pneumonia.” Chest (2010). PMID: 20382718 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism, 8. Long-term and Definitive Management, 12. Special Populations & Pregnancy - [63]
Feldman C, Anderson R. “Community-Acquired Pneumonia: Pathogenesis of Acute Cardiac Events and Potential Adjunctive Therapies.” Chest (2015). PMID: 25951315 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism, History and Evolution of Treatment, 12. Special Populations & Pregnancy - [64]
Peyrani P, Arnold FW, Bordon J et al.. “Incidence and Mortality of Adults Hospitalized With Community-Acquired Pneumonia According to Clinical Course.” Chest (2019). PMID: 31610158 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism, 8. Long-term and Definitive Management - [65]
Corrales-Medina VF, deKemp RA, Chirinos JA et al.. “Persistent Lung Inflammation After Clinical Resolution of Community-Acquired Pneumonia as Measured by 18FDG-PET/CT Imaging.” Chest (2021). PMID: 33667494 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism, History and Evolution of Treatment - [66]
Leung WS, Chu CM, Tsang KY et al.. “Fulminant community-acquired Acinetobacter baumannii pneumonia as a distinct clinical syndrome.” Chest (2006). PMID: 16424419 ↗
L3OTHERCited in: 2. Pathophysiology and Mechanism, 4. Clinical Presentation - [67]
Waterer GW, Kessler LA, Wunderink RG. “Delayed administration of antibiotics and atypical presentation in community-acquired pneumonia.” Chest (2006). PMID: 16840376 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism - [68]
Aliberti S, Amir A, Peyrani P et al.. “Incidence, etiology, timing, and risk factors for clinical failure in hospitalized patients with community-acquired pneumonia.” Chest (2008). PMID: 18583514 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism - [69]
Metersky ML, Ma A, Houck PM et al.. “Antibiotics for bacteremic pneumonia: Improved outcomes with macrolides but not fluoroquinolones.” Chest (2007). PMID: 17296649 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism - [70]
Pereira PC, de Lima CJ, Fernandes AB et al.. “Effects of photobiomodulation by infrared LED-therapy on improving cardiopulmonary functions and hematologic parameters in patients with community-acquired pneumonia (CAP).” Respiratory medicine (2026). PMID: 42009264 ↗
L1RCTCited in: 2. Pathophysiology and Mechanism, 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [71]
Zhou Y, Wei Y, Wang J et al.. “Efficacy and metabolomic analysis of the pneumonia compound formulation against community-acquired pneumonia: an observational controlled before-after clinical trial.” BMC infectious diseases (2025). PMID: 40165069 ↗
L1RCTCited in: 2. Pathophysiology and Mechanism - [72]
Grudzinska F, Faniyi AA, Belchamber KBR et al.. “Hospitalised older adults with community-acquired pneumonia and sepsis have dysregulated neutrophil function but preserved glycolysis.” Thorax (2025). PMID: 39689942 ↗
L3OTHERCited in: 2. Pathophysiology and Mechanism - [73]
Herr C, Beisswenger C, Hess C et al.. “Suppression of pulmonary innate host defence in smokers.” Thorax (2008). PMID: 18852155 ↗
L4OTHERCited in: 2. Pathophysiology and Mechanism - [74]
Violi F, Carnevale R, Calvieri C et al.. “Nox2 up-regulation is associated with an enhanced risk of atrial fibrillation in patients with pneumonia.” Thorax (2015). PMID: 26123660 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism, History and Evolution of Treatment - [75]
Wootton DG, Diggle PJ, Court J et al.. “Recovery from pneumonia requires efferocytosis which is impaired in smokers and those with low body mass index and enhanced by statins.” Thorax (2016). PMID: 27471049 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [76]
Yende S, van der Poll T, Lee M et al.. “The influence of pre-existing diabetes mellitus on the host immune response and outcome of pneumonia: analysis of two multicentre cohort studies.” Thorax (2010). PMID: 20861291 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism - [77]
Liu C, Yang X, Paoli-Bruno J et al.. “Allo-Priming Reverses Immunosenescence and May Restore Broad Respiratory Viral Protection and Vaccine Responsiveness to the Elderly: Results of a Phase I/II Clinical Trial.” Vaccines (2025). PMID: 40432075 ↗
L4TRIAL_NONRANDOMCited in: 2. Pathophysiology and Mechanism - [78]
Cillóniz C, Civljak R, Nicolini A et al.. “Polymicrobial community-acquired pneumonia: An emerging entity.” Respirology (Carlton, Vic.) (2015). PMID: 26494527 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism, 3. Epidemiology, Etiology and Risk Factors - [79]
Chen YH, Yao WZ, Gao JZ et al.. “Serum hydrogen sulfide as a novel marker predicting bacterial involvement in patients with community-acquired lower respiratory tract infections.” Respirology (Carlton, Vic.) (2009). PMID: 19659653 ↗
L3OTHERCited in: 2. Pathophysiology and Mechanism - [80]
Tagami T, Kushimoto S, Tosa R et al.. “Plasma neutrophil elastase correlates with pulmonary vascular permeability: a prospective observational study in patients with pneumonia.” Respirology (Carlton, Vic.) (2011). PMID: 21605276 ↗
L4OTHERCited in: 2. Pathophysiology and Mechanism - [81]
Wu M, Han S, Li H. “Lefamulin versus omadacycline for community acquired bacterial pneumonia: a systematic review and anchored indirect treatment comparison using moxifloxacin as the common comparator.” Journal of comparative effectiveness research (2026). PMID: 41823576 ↗
L1SR_OBSCited in: 2. Pathophysiology and Mechanism - [82]
Georgakopoulou VE, Dodos K, Pitiriga VC. “Role of Lipidomics in Respiratory Tract Infections: A Systematic Review of Emerging Evidence.” Microorganisms (2025). PMID: 41011521 ↗
L5SR_OBSCited in: 2. Pathophysiology and Mechanism - [83]
Pott H, Gaffron S, Martin R et al.. “Self-organising map clustering identifies high-risk clusters of post-acute mortality in a prospective multicentre study of community-acquired pneumonia.” ERJ open research (2026). PMID: 41561102 ↗
L2OTHERCited in: 2. Pathophysiology and Mechanism - [84]
Steven Yi BS, Saurav Sumughan BS, Jessica Cobb MD et al.. “Fluoroquinolone Use and Risk of Pneumothorax in Adults Hospitalized With Community Acquired Pneumonia: A Retrospective Cohort Study.” The clinical respiratory journal (2026). PMID: 42387596 ↗
L2COHORTCited in: 2. Pathophysiology and Mechanism, 10. Complications - [85]
Ke Q, Zhao C, Luo S et al.. “Effect of the maxing huoqiao granule on nonsevere community-acquired pneumonia: A multicenter, double-blind, placebo-controlled randomized trial.” Pharmacological research (2026). PMID: 41966499 ↗
L1RCTCited in: 2. Pathophysiology and Mechanism - [86]
Luo H, Zeng Q, Xie N et al.. “Coordinated Regulation of TLR2 Signaling by Neu1 Sialidase and the Siglec-5/Siglec-14 Receptor Pair During Mycoplasma pneumoniae Infection.” ACS infectious diseases (2026). PMID: 42350323 ↗
L5OTHERCited in: 2. Pathophysiology and Mechanism - [87]
Feldman C, Richards GA. “The Impact of Environmental and Climate Factors on Pneumonia Pathogenesis.” Clinics in chest medicine (2026). PMID: 42203411 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism - [88]
Tu S, Li Y, Zhou Y et al.. “Chlamydia beyond the genital tract: a major contributor to community-acquired pneumonia.” Frontiers in cellular and infection microbiology (2026). PMID: 42180254 ↗
L5REVIEW_NARRATIVECited in: 2. Pathophysiology and Mechanism - [89]
Wunderink RG, Laterre PF, Francois B et al.. “Recombinant tissue factor pathway inhibitor in severe community-acquired pneumonia: a randomized trial.” American journal of respiratory and critical care medicine (2011). PMID: 21297074 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [90]
Wirz SA, Blum CA, Schuetz P et al.. “Pathogen- and antibiotic-specific effects of prednisone in community-acquired pneumonia.” The European respiratory journal (2016). PMID: 27471201 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 10. Complications, 11. Prognosis and Natural History - [91]
Heming N, Renault A, Kuperminc E et al.. “Hydrocortisone plus fludrocortisone for community acquired pneumonia-related septic shock: a subgroup analysis of the APROCCHSS phase 3 randomised trial.” The Lancet. Respiratory medicine (2024). PMID: 38310918 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [92]
Wilson KC, Schünemann HJ. “An appraisal of the evidence underlying performance measures for community-acquired pneumonia.” American journal of respiratory and critical care medicine (2011). PMID: 21239689 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 13. Prevention, Screening & Surveillance - [93]
Chalmers JD, Akram AR, Hill AT. “Increasing outpatient treatment of mild community-acquired pneumonia: systematic review and meta-analysis.” The European respiratory journal (2010). PMID: 20729221 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [94]
Dequin PF, Meziani F, Quenot JP et al.. “Hydrocortisone in Severe Community-Acquired Pneumonia.” The New England journal of medicine (2023). PMID: 36942789 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [95]
Lucinde RK, Gathuri H, Mwaniki P et al.. “A Pragmatic Trial of Glucocorticoids for Community-Acquired Pneumonia.” The New England journal of medicine (2025). PMID: 41159889 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [96]
Postma DF, van Werkhoven CH, van Elden LJ et al.. “Antibiotic treatment strategies for community-acquired pneumonia in adults.” The New England journal of medicine (2015). PMID: 25830421 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [97]
Smit JM, Van Der Zee PA, Stoof SCM et al.. “Predicting benefit from adjuvant therapy with corticosteroids in community-acquired pneumonia: a data-driven analysis of randomised trials.” The Lancet. Respiratory medicine (2025). PMID: 39892408 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [98]
Saleem N, Kulkarni A, Snow TAC et al.. “Effect of Corticosteroids on Mortality and Clinical Cure in Community-Acquired Pneumonia: A Systematic Review, Meta-analysis, and Meta-regression of Randomized Control Trials.” Chest (2022). PMID: 36087797 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [99]
Fernandez Elviro C, Longcroft-Harris B, Allin E et al.. “Conservative and Surgical Modalities in the Management of Pediatric Parapneumonic Effusion and Empyema: A Living Systematic Review and Network Meta-Analysis.” Chest (2023). PMID: 37463660 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 8. Long-term and Definitive Management, 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive), 10. Complications, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [100]
Wan YD, Sun TW, Liu ZQ et al.. “Efficacy and Safety of Corticosteroids for Community-Acquired Pneumonia: A Systematic Review and Meta-Analysis.” Chest (2016). PMID: 26501852 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [101]
Schauwvlieghe AFAD, Rijnders BJA, Philips N et al.. “Invasive aspergillosis in patients admitted to the intensive care unit with severe influenza: a retrospective cohort study.” The Lancet. Respiratory medicine (2018). PMID: 30076119 ↗
L3COHORTCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 10. Complications, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [102]
Bai AD, Srivastava S, Digby GC et al.. “Anaerobic Antibiotic Coverage in Aspiration Pneumonia and the Associated Benefits and Harms: A Retrospective Cohort Study.” Chest (2024). PMID: 38387648 ↗
L3COHORTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [103]
Montes-Andujar L, Tinoco E, Baez-Pravia O et al.. “Empiric antibiotics for community-acquired pneumonia in adult patients: a systematic review and a network meta-analysis.” Thorax (2021). PMID: 33723019 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [104]
Loke YK, Kwok CS, Niruban A et al.. “Value of severity scales in predicting mortality from community-acquired pneumonia: systematic review and meta-analysis.” Thorax (2010). PMID: 20729235 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [105]
Ruopp M, Chiswell K, Thaden JT et al.. “Respiratory Tract Infection Clinical Trials from 2007 to 2012. A Systematic Review of ClinicalTrials.gov.” Annals of the American Thoracic Society (2015). PMID: 26360527 ↗
L5TRIAL_NONRANDOMCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [106]
Angus DC, Berry S, Lewis RJ et al.. “The REMAP-CAP (Randomized Embedded Multifactorial Adaptive Platform for Community-acquired Pneumonia) Study. Rationale and Design.” Annals of the American Thoracic Society (2020). PMID: 32267771 ↗
L5TRIAL_NONRANDOMCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [107]
Liu D, Su LX, Guan W et al.. “Prognostic value of procalcitonin in pneumonia: A systematic review and meta-analysis.” Respirology (Carlton, Vic.) (2015). PMID: 26662169 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [108]
Wang M, Cai F, Wu X et al.. “Incidence of viral infection detected by PCR and real-time PCR in childhood community-acquired pneumonia: a meta-analysis.” Respirology (Carlton, Vic.) (2015). PMID: 25615588 ↗
L4SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors - [109]
Jiang HL, Chen HX, Liu W et al.. “Is COPD associated with increased mortality and morbidity in hospitalized pneumonia? A systematic review and meta-analysis.” Respirology (Carlton, Vic.) (2015). PMID: 26177049 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [110]
Horita N, Otsuka T, Haranaga S et al.. “Beta-lactam plus macrolides or beta-lactam alone for community-acquired pneumonia: A systematic review and meta-analysis.” Respirology (Carlton, Vic.) (2016). PMID: 27338144 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [111]
Blanc PD, Annesi-Maesano I, Balmes JR et al.. “The Occupational Burden of Nonmalignant Respiratory Diseases. An Official American Thoracic Society and European Respiratory Society Statement.” American journal of respiratory and critical care medicine (2019). PMID: 31149852 ↗
L1REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors - [112]
Chouchane O, Schuurman AR, Reijnders TDY et al.. “The Plasma Lipidomic Landscape in Patients with Sepsis due to Community-acquired Pneumonia.” American journal of respiratory and critical care medicine (2024). PMID: 38240721 ↗
L3OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 6. Severity, Staging and Risk Stratification, 10. Complications, 11. Prognosis and Natural History - [113]
Eurich DT, Marrie TJ, Minhas-Sandhu JK et al.. “Ten-Year Mortality after Community-acquired Pneumonia. A Prospective Cohort.” American journal of respiratory and critical care medicine (2015). PMID: 26067221 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, 11. Prognosis and Natural History - [114]
Gutbier B, Neuhauß AK, Reppe K et al.. “Prognostic and Pathogenic Role of Angiopoietin-1 and -2 in Pneumonia.” American journal of respiratory and critical care medicine (2018). PMID: 29447449 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [115]
Aston SJ, Ho A, Jary H et al.. “Etiology and Risk Factors for Mortality in an Adult Community-acquired Pneumonia Cohort in Malawi.” American journal of respiratory and critical care medicine (2019). PMID: 30625278 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification - [116]
Kobe H, Momose M, Miyazaki Y et al.. “A 73-Year-Old Man With Refractory Hemoptysis.” Chest (2022). PMID: 36210108 ↗
L4CASE_REPORTCited in: 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 7. Acute Management and Exacerbation Rescue, History and Evolution of Treatment - [117]
Frencken JF, van Baal L, Kappen TH et al.. “Myocardial Injury in Critically Ill Patients with Community-acquired Pneumonia. A Cohort Study.” Annals of the American Thoracic Society (2019). PMID: 30521759 ↗
L3COHORTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue - [118]
Jensen AV, Baunbæk Egelund G, Bang Andersen S et al.. “The Glycemic Gap and 90-Day Mortality in Community-acquired Pneumonia. A Prospective Cohort Study.” Annals of the American Thoracic Society (2019). PMID: 31437014 ↗
L2COHORTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [119]
Martin-Loeches I, Torres A, Nagavci B et al.. “ERS/ESICM/ESCMID/ALAT guidelines for the management of severe community-acquired pneumonia.” The European respiratory journal (2023). PMID: 37012080 ↗
L1OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [120]
de Roux A, Ewig S, García E et al.. “Mixed community-acquired pneumonia in hospitalised patients.” The European respiratory journal (2006). PMID: 16585087 ↗
L4OTHERCited in: 3. Epidemiology, Etiology and Risk Factors - [121]
Gillet Y, Tristan A, Rasigade JP et al.. “Prognostic factors of severe community-acquired staphylococcal pneumonia in France.” The European respiratory journal (2021). PMID: 33833037 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 6. Severity, Staging and Risk Stratification, History and Evolution of Treatment, 11. Prognosis and Natural History - [122]
Pereverzeva L, Uhel F, Peters Sengers H et al.. “Blood leukocyte transcriptomes in Gram-positive and Gram-negative community-acquired pneumonia.” The European respiratory journal (2022). PMID: 34446464 ↗
L4OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [123]
Nouailles G, Bischoff R, Linke K et al.. “Trimodulin supports antibacterial defence and restricts inflammation in preclinical pneumonia models.” The European respiratory journal (2026). PMID: 40935582 ↗
L5OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification - [124]
Jensen AV, Egelund GB, Andersen SB et al.. “The impact of blood glucose on community-acquired pneumonia: a retrospective cohort study.” ERJ open research (2017). PMID: 28656133 ↗
L3COHORTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [125]
Lac J, Han S, Ahmad M et al.. “Low-dose corticosteroids in severe pulmonary infection: a meta-analysis of randomised controlled trials.” BMJ open respiratory research (2026). PMID: 42425738 ↗
L1SR_MA_RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [126]
Singanayagam A, Chalmers JD. “Severity assessment scores to guide empirical use of antibiotics in community acquired pneumonia.” The Lancet. Respiratory medicine (2013). PMID: 24461668 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 10. Complications, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [127]
Marik PE. “The role of glucocorticoids as adjunctive treatment for sepsis in the modern era.” The Lancet. Respiratory medicine (2018). PMID: 30006071 ↗
L5OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [128]
Cilloniz C, Ward L, Mogensen ML et al.. “Machine-Learning Model for Mortality Prediction in Patients With Community-Acquired Pneumonia: Development and Validation Study.” Chest (2022). PMID: 35850287 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [129]
Marin-Corral J, Pascual-Guardia S, Amati F et al.. “Aspiration Risk Factors, Microbiology, and Empiric Antibiotics for Patients Hospitalized With Community-Acquired Pneumonia.” Chest (2020). PMID: 32687909 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, History and Evolution of Treatment - [130]
Menendez R, Torres A. “Treatment failure in community-acquired pneumonia.” Chest (2007). PMID: 17934120 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive), 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [131]
Cilloniz C, Pericàs JM, Restrepo MI. “Community-Acquired Pneumonia in Nursing-Home Residents in the Post-HCAP Era.” Chest (2026). PMID: 42425406 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [132]
Fujitani S, Sun HY, Yu VL et al.. “Pneumonia due to Pseudomonas aeruginosa: part I: epidemiology, clinical diagnosis, and source.” Chest (2011). PMID: 21467058 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [133]
Gohil SK, Avery TR, Kleinman K et al.. “Improving Empiric Antibiotic Selection for Patients With Cancer Hospitalized With Infection: Secondary Analysis of the INSPIRE Cluster Randomized Trials.” JAMA network open (2026). PMID: 42268612 ↗
L2RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [134]
Freiberg JA, Qian ET, Nairon KG et al.. “Swab Testing to Optimize Pneumonia Treatment With Empiric Vancomycin: A Randomized Controlled Trial.” Clinical infectious diseases : an official publication of the Infectious Diseases Society of America (2026). PMID: 42227019 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [135]
Jain S, Self WH, Wunderink RG et al.. “Community-Acquired Pneumonia Requiring Hospitalization among U.S. Adults.” The New England journal of medicine (2015). PMID: 26172429 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 13. Prevention, Screening & Surveillance - [136]
Jain S, Williams DJ, Arnold SR et al.. “Community-acquired pneumonia requiring hospitalization among U.S. children.” The New England journal of medicine (2015). PMID: 25714161 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 13. Prevention, Screening & Surveillance - [137]
Martin-Loeches I, Reyes LF, Rodriguez A. “Severe community-acquired pneumonia (sCAP): advances in management and future directions.” Thorax (2025). PMID: 40360263 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [138]
Torres A, Blasi F, Dartois N et al.. “Which individuals are at increased risk of pneumococcal disease and why? Impact of COPD, asthma, smoking, diabetes, and/or chronic heart disease on community-acquired pneumonia and invasive pneumococcal disease.” Thorax (2015). PMID: 26219979 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 8. Long-term and Definitive Management, 11. Prognosis and Natural History, 13. Prevention, Screening & Surveillance - [139]
Grudzinska FS, Brodlie M, Scholefield BR et al.. “Neutrophils in community-acquired pneumonia: parallels in dysfunction at the extremes of age.” Thorax (2019). PMID: 31732687 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 13. Prevention, Screening & Surveillance - [140]
Torres A, Peetermans WE, Viegi G et al.. “Risk factors for community-acquired pneumonia in adults in Europe: a literature review.” Thorax (2013). PMID: 24130229 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [141]
Welte T, Torres A, Nathwani D. “Clinical and economic burden of community-acquired pneumonia among adults in Europe.” Thorax (2010). PMID: 20729232 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 8. Long-term and Definitive Management, 11. Prognosis and Natural History - [142]
Lawrence H, McKeever TM, Lim WS. “Readmission following hospital admission for community-acquired pneumonia in England.” Thorax (2023). PMID: 37524392 ↗
L3OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [143]
Takeda K, Takazono T, Ashizawa N et al.. “Lascufloxacin switch therapy versus ampicillin/sulbactam for older patients with community-acquired pneumonia in Japan (STEP study): a study protocol for a multicentre open-label randomised controlled non-inferiority trial.” BMJ open (2026). PMID: 42379706 ↗
L5TRIAL_NONRANDOMCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 8. Long-term and Definitive Management, 10. Complications, 11. Prognosis and Natural History - [144]
Choi YY, Kang C, Choe YJ et al.. “Efficacy and safety of Doxycycline versus Macrolides for Mycoplasma pneumoniae INfectiOn in Children (DOMINO): a protocol for a multicentre, randomised, open-label, superiority trial.” BMJ open (2026). PMID: 42191206 ↗
L5TRIAL_NONRANDOMCited in: 3. Epidemiology, Etiology and Risk Factors, 11. Prognosis and Natural History - [145]
Wang H, Dou H, Chen G et al.. “Efficacy and Safety of Lianhua Qingke Tablets in Children With Mycoplasma pneumoniae Pneumonia: A Randomized, Double-Blind, Multicenter, Placebo-Controlled Clinical Trial.” The clinical respiratory journal (2026). PMID: 42357817 ↗
L1RCTCited in: 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [146]
Ouyang Y, Lai J, Wang P et al.. “Efficacy of higher-dose versus lower-dose corticosteroids in community-acquired pneumonia: a systematic review and network meta-analysis.” Critical care (London, England) (2026). PMID: 42402602 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [147]
Pitrowsky M, Pacheco MB, Ranzani O et al.. “Outcomes of Pneumonia in ICUs in Low- and Middle-Income Countries - A Systematic Review.” NEJM evidence (2026). PMID: 42189048 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [148]
Korang SK, Nava C, Mohana SP et al.. “Antibiotics for hospital-acquired pneumonia in neonates and children.” The Cochrane database of systematic reviews (2021). PMID: 34727368 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [149]
Lodha R, Kabra SK, Pandey RM. “Antibiotics for community-acquired pneumonia in children.” The Cochrane database of systematic reviews (2013). PMID: 23733365 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [150]
Kabra SK, Lodha R, Pandey RM. “Antibiotics for community-acquired pneumonia in children.” The Cochrane database of systematic reviews (2010). PMID: 20238334 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [151]
Kabra SK, Lodha R, Pandey RM. “Antibiotics for community acquired pneumonia in children.” The Cochrane database of systematic reviews (2006). PMID: 16856067 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [152]
Martí-Carvajal AJ, Conterno LO. “Antibiotics for treating community-acquired pneumonia in people with sickle cell disease.” The Cochrane database of systematic reviews (2016). PMID: 27841444 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 10. Complications, 11. Prognosis and Natural History - [153]
Walters JA, Tang JN, Poole P et al.. “Pneumococcal vaccines for preventing pneumonia in chronic obstructive pulmonary disease.” The Cochrane database of systematic reviews (2017). PMID: 28116747 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History, 13. Prevention, Screening & Surveillance - [154]
Zhang Y, Fang C, Dong BR et al.. “Oxygen therapy for pneumonia in adults.” The Cochrane database of systematic reviews (2012). PMID: 22419316 ↗
L1SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 10. Complications, 11. Prognosis and Natural History - [155]
Martí-Carvajal AJ, Conterno LO. “Antibiotics for treating community acquired pneumonia in people with sickle cell disease.” The Cochrane database of systematic reviews (2012). PMID: 23076916 ↗
L2SR_OBSCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 10. Complications - [156]
Santoso P, Muliandini GR, Izzati SD et al.. “Antimicrobial Resistance and Clinical Outcome Among Hospitalized Bacterial Pneumonia: A Retrospective Cohort Study in Indonesian Tertiary Hospital.” Antibiotics (Basel, Switzerland) (2026). PMID: 42353706 ↗
L2COHORTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 13. Prevention, Screening & Surveillance - [157]
Nasr R, Rahal EA, Haddad C et al.. “Assessment of Compliance with National and International Guidelines in the Empirical Management of Community-Acquired Pneumonia (CAP) in Lebanese Hospitals: A Multicenter Retrospective Cohort Study.” Antibiotics (Basel, Switzerland) (2026). PMID: 42353675 ↗
L2COHORTCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification - [158]
Cilloniz C, Ewig S, Gabarrus A et al.. “Seasonality of pathogens causing community-acquired pneumonia.” Respirology (Carlton, Vic.) (2017). PMID: 28093834 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors - [159]
Hadfield J, Bennett L. “Determining best outcomes from community-acquired pneumonia and how to achieve them.” Respirology (Carlton, Vic.) (2017). PMID: 29150897 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [160]
Mecham ID, Vines C, Dean NC. “Community-acquired pneumonia management and outcomes in the era of health information technology.” Respirology (Carlton, Vic.) (2017). PMID: 28758325 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [161]
Niederman MS. “Making sense of scoring systems in community acquired pneumonia.” Respirology (Carlton, Vic.) (2009). PMID: 19353770 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [162]
Jeon K, Yoo H, Jeong BH et al.. “Functional status and mortality prediction in community-acquired pneumonia.” Respirology (Carlton, Vic.) (2017). PMID: 28513919 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [163]
Mattila JT, Fine MJ, Limper AH et al.. “Pneumonia. Treatment and diagnosis.” Annals of the American Thoracic Society (2014). PMID: 25148424 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [164]
Malo J, Luraschi-Monjagatta C, Wolk DM et al.. “Update on the diagnosis of pulmonary coccidioidomycosis.” Annals of the American Thoracic Society (2014). PMID: 24575994 ↗
L5REVIEW_NARRATIVECited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 8. Long-term and Definitive Management, 10. Complications, 12. Special Populations & Pregnancy - [165]
Jones BE, Ying J, Nevers M et al.. “Computerized Mortality Prediction for Community-acquired Pneumonia at 117 Veterans Affairs Medical Centers.” Annals of the American Thoracic Society (2021). PMID: 33635750 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [166]
Prina E, Ranzani OT, Polverino E et al.. “Risk factors associated with potentially antibiotic-resistant pathogens in community-acquired pneumonia.” Annals of the American Thoracic Society (2015). PMID: 25521229 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [167]
Sando E, Suzuki M, Ishida M et al.. “Definitive and Indeterminate Pseudomonas aeruginosa Infection in Adults with Community-acquired Pneumonia: A Prospective Observational Study.” Annals of the American Thoracic Society (2021). PMID: 33565942 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, History and Evolution of Treatment, 11. Prognosis and Natural History - [168]
Cangemi R, Falcone M, Taliani G et al.. “Corticosteroid Use and Incident Myocardial Infarction in Adults Hospitalized for Community-acquired Pneumonia.” Annals of the American Thoracic Society (2019). PMID: 30188173 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [169]
Chouchane O, Léopold V, Michels EHA et al.. “Differential platelet protein release profiles in community-acquired pneumonia and COVID-19.” ERJ open research (2025). PMID: 40551807 ↗
L3OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [170]
Farhat I, Rosolowski M, Ahrens K et al.. “Biomarkers troponin and procalcitonin in addition to CRB-65 enhance risk stratification in patients with community-acquired pneumonia.” ERJ open research (2024). PMID: 39624382 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [171]
Richter T, Tesch F, Schmitt J et al.. “Validation of the qSOFA and CRB-65 in SARS-CoV-2-infected community-acquired pneumonia.” ERJ open research (2023). PMID: 37337510 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [172]
Prat-Aymerich C, Hessels L, Karssen D et al.. “Rationale and design of the Pneumococcal Pneumonia Epidemiology, Urine Serotyping and Mental Outcomes (PNEUMO) study Europe.” ERJ open research (2025). PMID: 41367668 ↗
L5OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 13. Prevention, Screening & Surveillance - [173]
Cilloniz C, Mogensen ML, Ward L. “Transforming post-acute pneumonia management: risk stratification using machine learning.” ERJ open research (2026). PMID: 41561110 ↗
L5OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [174]
Wittermans E, van der Zee PA, Qi H et al.. “Community-acquired pneumonia subgroups and differential response to corticosteroids: a secondary analysis of controlled studies.” ERJ open research (2022). PMID: 35036417 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 4. Clinical Presentation, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [175]
Rademacher J, von Eynern L, Dettmer S et al.. “Performance of risk prediction scores for severe pneumonia in patients with community-acquired pneumonia after organ transplantation.” ERJ open research (2025). PMID: 41122418 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 8. Long-term and Definitive Management, 11. Prognosis and Natural History - [176]
Kaal AG, Op de Hoek L, Hochheimer DT et al.. “Outcomes of community-acquired pneumonia using the Pneumonia Severity Index versus the CURB-65 in routine practice of emergency departments.” ERJ open research (2023). PMID: 37143846 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 11. Prognosis and Natural History - [177]
Nemoto M, Nakashima K, Noma S et al.. “Prognostic value of chest computed tomography in community-acquired pneumonia patients.” ERJ open research (2020). PMID: 33263023 ↗
L2OTHERCited in: 3. Epidemiology, Etiology and Risk Factors, 6. Severity, Staging and Risk Stratification - [178]
Fitzgerald DB, Waterer GW, Budgeon C et al.. “Steroid Therapy and Outcome of Parapneumonic Pleural Effusions (STOPPE): A Pilot Randomized Clinical Trial.” American journal of respiratory and critical care medicine (2022). PMID: 35081010 ↗
L1RCTCited in: 4. Clinical Presentation, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [179]
Paul M, Nielsen AD, Gafter-Gvili A et al.. “The need for macrolides in hospitalised community-acquired pneumonia: propensity analysis.” The European respiratory journal (2007). PMID: 17537772 ↗
L2RCTCited in: 4. Clinical Presentation, 8. Long-term and Definitive Management, History and Evolution of Treatment - [180]
Pick HJ, Bolton CE, Lim WS et al.. “Patient-reported outcome measures in the recovery of adults hospitalised with community-acquired pneumonia: a systematic review.” The European respiratory journal (2019). PMID: 30635298 ↗
L2SR_OBSCited in: 4. Clinical Presentation, 11. Prognosis and Natural History - [181]
Atkinson M, Lakhanpaul M, Smyth A et al.. “Comparison of oral amoxicillin and intravenous benzyl penicillin for community acquired pneumonia in children (PIVOT trial): a multicentre pragmatic randomised controlled equivalence trial.” Thorax (2007). PMID: 17567657 ↗
L1RCTCited in: 4. Clinical Presentation, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 10. Complications - [182]
Cillóniz C, Torres A, Manzardo C et al.. “Community-Acquired Pneumococcal Pneumonia in Virologically Suppressed HIV-Infected Adult Patients: A Matched Case-Control Study.” Chest (2017). PMID: 28302496 ↗
L3CASE_CONTROLCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 13. Prevention, Screening & Surveillance - [183]
Polverino E, Torres A, Menendez R et al.. “Microbial aetiology of healthcare associated pneumonia in Spain: a prospective, multicentre, case-control study.” Thorax (2013). PMID: 24130227 ↗
L3CASE_CONTROLCited in: 4. Clinical Presentation - [184]
Méndez R, Menéndez R, Cillóniz C et al.. “Initial Inflammatory Profile in Community-acquired Pneumonia Depends on Time since Onset of Symptoms.” American journal of respiratory and critical care medicine (2018). PMID: 29509439 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [185]
Shindo Y, Ito R, Kobayashi D et al.. “Risk factors for drug-resistant pathogens in community-acquired and healthcare-associated pneumonia.” American journal of respiratory and critical care medicine (2013). PMID: 23855620 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [186]
España PP, Capelastegui A, Gorordo I et al.. “Development and validation of a clinical prediction rule for severe community-acquired pneumonia.” American journal of respiratory and critical care medicine (2006). PMID: 16973986 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [187]
Christ-Crain M, Stolz D, Jutla S et al.. “Free and total cortisol levels as predictors of severity and outcome in community-acquired pneumonia.” American journal of respiratory and critical care medicine (2007). PMID: 17702966 ↗
L2OTHERCited in: 4. Clinical Presentation - [188]
Cilloniz C, Albert RK, Liapikou A et al.. “The Effect of Macrolide Resistance on the Presentation and Outcome of Patients Hospitalized for Streptococcus pneumoniae Pneumonia.” American journal of respiratory and critical care medicine (2015). PMID: 25807239 ↗
L2OTHERCited in: 4. Clinical Presentation, 10. Complications - [189]
Yende S, D'Angelo G, Kellum JA et al.. “Inflammatory markers at hospital discharge predict subsequent mortality after pneumonia and sepsis.” American journal of respiratory and critical care medicine (2008). PMID: 18369199 ↗
L2OTHERCited in: 4. Clinical Presentation - [190]
Quigley N, Couture C, Gervais P et al.. “A 37-Year-Old Man With Right Lung Consolidation.” Chest (2023). PMID: 36894264 ↗
L4CASE_REPORTCited in: 4. Clinical Presentation, 7. Acute Management and Exacerbation Rescue, History and Evolution of Treatment, 10. Complications - [191]
Wang H, Tang Y, Shen Y. “Late-Onset Diffuse Lung Disease in an 8-Year-Old Girl.” Chest (2024). PMID: 38461021 ↗
L4CASE_REPORTCited in: 4. Clinical Presentation, History and Evolution of Treatment - [192]
Ko MY, Guzner A, Saini I. “A 19-Year-Old With Hemoptysis and Shortness of Breath.” Chest (2023). PMID: 37945196 ↗
L4CASE_REPORTCited in: 4. Clinical Presentation, History and Evolution of Treatment - [193]
Cilloniz C, Torres A, Polverino E et al.. “Community-acquired lung respiratory infections in HIV-infected patients: microbial aetiology and outcome.” The European respiratory journal (2014). PMID: 24525448 ↗
L2OTHERCited in: 4. Clinical Presentation - [194]
Liapikou A, Polverino E, Ewig S et al.. “Severity and outcomes of hospitalised community-acquired pneumonia in COPD patients.” The European respiratory journal (2011). PMID: 21920895 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 10. Complications - [195]
Klapdor B, Ewig S, Pletz MW et al.. “Community-acquired pneumonia in younger patients is an entity on its own.” The European respiratory journal (2011). PMID: 22088967 ↗
L2OTHERCited in: 4. Clinical Presentation, 8. Long-term and Definitive Management, 12. Special Populations & Pregnancy - [196]
von Baum H, Welte T, Marre R et al.. “Community-acquired pneumonia through Enterobacteriaceae and Pseudomonas aeruginosa: Diagnosis, incidence and predictors.” The European respiratory journal (2009). PMID: 19679601 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [197]
Garcia-Vidal C, Fernández-Sabé N, Carratalà J et al.. “Early mortality in patients with community-acquired pneumonia: causes and risk factors.” The European respiratory journal (2008). PMID: 18508820 ↗
L2OTHERCited in: 4. Clinical Presentation, 10. Complications, 12. Special Populations & Pregnancy - [198]
Ho PL, Cheng VC, Chu CM. “Antibiotic resistance in community-acquired pneumonia caused by Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus, and Acinetobacter baumannii.” Chest (2009). PMID: 19809053 ↗
L5REVIEW_NARRATIVECited in: 4. Clinical Presentation, 10. Complications - [199]
Upchurch CP, Grijalva CG, Wunderink RG et al.. “Community-Acquired Pneumonia Visualized on CT Scans but Not Chest Radiographs: Pathogens, Severity, and Clinical Outcomes.” Chest (2017). PMID: 28802696 ↗
L2OTHERCited in: 4. Clinical Presentation, 13. Prevention, Screening & Surveillance - [200]
Malhotra A. “Low-tidal-volume ventilation in the acute respiratory distress syndrome.” The New England journal of medicine (2007). PMID: 17855672 ↗
L4REVIEW_NARRATIVECited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue - [201]
Kolditz M, Ewig S, Klapdor B et al.. “Community-acquired pneumonia as medical emergency: predictors of early deterioration.” Thorax (2015). PMID: 25782758 ↗
L2OTHERCited in: 4. Clinical Presentation, 7. Acute Management and Exacerbation Rescue - [202]
Ewig S, Klapdor B, Pletz MW et al.. “Nursing-home-acquired pneumonia in Germany: an 8-year prospective multicentre study.” Thorax (2011). PMID: 22058186 ↗
L2OTHERCited in: 4. Clinical Presentation, 8. Long-term and Definitive Management - [203]
Chalmers JD, Singanayagam A, Murray MP et al.. “Risk factors for complicated parapneumonic effusion and empyema on presentation to hospital with community-acquired pneumonia.” Thorax (2009). PMID: 19131449 ↗
L2OTHERCited in: 4. Clinical Presentation, History and Evolution of Treatment - [204]
Buising KL, Thursky KA, Black JF et al.. “A prospective comparison of severity scores for identifying patients with severe community acquired pneumonia: reconsidering what is meant by severe pneumonia.” Thorax (2006). PMID: 16449258 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [205]
Ong CW, Lye DC, Khoo KL et al.. “Severe community-acquired Acinetobacter baumannii pneumonia: an emerging highly lethal infectious disease in the Asia-Pacific.” Respirology (Carlton, Vic.) (2009). PMID: 19909464 ↗
L4CASE_REPORTCited in: 4. Clinical Presentation, 10. Complications - [206]
Wang C, Gao H, Zhu C et al.. “Safety of proton pump inhibitors: an overview of systematic reviews and meta-analyses.” BMJ evidence-based medicine (2026). PMID: 42303374 ↗
L5SR_OBSCited in: 4. Clinical Presentation, 11. Prognosis and Natural History - [207]
Lassi ZS, Imdad A, Bhutta ZA. “Short-course versus long-course intravenous therapy with the same antibiotic for severe community-acquired pneumonia in children aged two months to 59 months.” The Cochrane database of systematic reviews (2017). PMID: 29020436 ↗
L1SR_OBSCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [208]
Lassi ZS, Imdad A, Bhutta ZA. “Short-course versus long-course intravenous therapy with the same antibiotic for severe community-acquired pneumonia in children aged two months to 59 months.” The Cochrane database of systematic reviews (2015). PMID: 26077639 ↗
L1SR_OBSCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [209]
Wang K, Gill P, Perera R et al.. “Clinical symptoms and signs for the diagnosis of Mycoplasma pneumoniae in children and adolescents with community-acquired pneumonia.” The Cochrane database of systematic reviews (2012). PMID: 23076954 ↗
L1SR_OBSCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [210]
Huang Y, Lin Q. “A novel risk stratification model based on creatine kinase and direct bilirubin for identifying severe Chlamydia psittaci pneumonia: a double-center, hypothesis-generating retrospective cohort study.” BMC infectious diseases (2026). PMID: 42249297 ↗
L2COHORTCited in: 4. Clinical Presentation, 6. Severity, Staging and Risk Stratification - [211]
Wang F, Han A, Hong W et al.. “Comparison of targeted next-generation sequencing and conventional tests for pathogen detection in community-acquired and severe community-acquired pneumonia: a retrospective cohort study.” Frontiers in microbiology (2026). PMID: 42199547 ↗
L2COHORTCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [212]
Cochand L, Bürgisser N, Buclin CP et al.. “Frank's Sign and Risk of Cardiovascular Events in Patients Hospitalized for Pneumonia: A Prospective Single-Center Cohort Study.” Journal of clinical medicine (2026). PMID: 42194618 ↗
L2COHORTCited in: 4. Clinical Presentation, 10. Complications - [213]
Liu L, Wang J, Jiang W et al.. “Clinical characteristics and risk factors for severe community-acquired pneumonia in hospitalized children with human metapneumovirus infection in Shanghai: a retrospective cohort study.” Frontiers in medicine (2026). PMID: 42145772 ↗
L2COHORTCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 12. Special Populations & Pregnancy - [214]
Li Y, Zhu H, Zhan Z et al.. “Clinical features and prognostic factors of Chlamydia psittaci pneumonia: a retrospective study.” Frontiers in medicine (2026). PMID: 42006869 ↗
L2COHORTCited in: 4. Clinical Presentation - [215]
Thomas R, Ferguson J, Coombs G et al.. “Community-acquired methicillin-resistant Staphylococcus aureus pneumonia: a clinical audit.” Respirology (Carlton, Vic.) (2011). PMID: 21382130 ↗
L4OTHERCited in: 4. Clinical Presentation, 10. Complications - [216]
Seo H, Cha SI, Shin KM et al.. “Clinical relevance of necrotizing change in patients with community-acquired pneumonia.” Respirology (Carlton, Vic.) (2016). PMID: 27862706 ↗
L2OTHERCited in: 4. Clinical Presentation - [217]
Liam CK, Pang YK, Poosparajah S. “Pulmonary tuberculosis presenting as community-acquired pneumonia.” Respirology (Carlton, Vic.) (2006). PMID: 17052309 ↗
L2OTHERCited in: 4. Clinical Presentation, History and Evolution of Treatment, 12. Special Populations & Pregnancy - [218]
Sibila O, Laserna E, Maselli DJ et al.. “Risk factors and antibiotic therapy in P. aeruginosa community-acquired pneumonia.” Respirology (Carlton, Vic.) (2015). PMID: 25776134 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification - [219]
Falguera M, Carratalà J, Ruiz-Gonzalez A et al.. “Risk factors and outcome of community-acquired pneumonia due to Gram-negative bacilli.” Respirology (Carlton, Vic.) (2009). PMID: 18699803 ↗
L2OTHERCited in: 4. Clinical Presentation - [220]
Polverino E, Cillóniz C, Dambrava P et al.. “Systemic corticosteroids for community-acquired pneumonia: reasons for use and lack of benefit on outcome.” Respirology (Carlton, Vic.) (2013). PMID: 23134361 ↗
L2OTHERCited in: 4. Clinical Presentation, 7. Acute Management and Exacerbation Rescue - [221]
Sanz F, Restrepo MI, Fernández-Fabrellas E et al.. “Does prolonged onset of symptoms have a prognostic significance in community-acquired pneumonia?” Respirology (Carlton, Vic.) (2014). PMID: 24995803 ↗
L2OTHERCited in: 4. Clinical Presentation, 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 10. Complications - [222]
D'Agostino S, Granberg V, Valentini G et al.. “Mucositis Associated with Mycoplasma pneumoniae: Systematic Review and Case Series.” Children (Basel, Switzerland) (2026). PMID: 42194164 ↗
L2SR_OBSCited in: 4. Clinical Presentation, 10. Complications - [223]
Wetzke M, Schütz K, Kopp MV et al.. “Pathogen spectra in hospitalised and nonhospitalised children with community-acquired pneumonia.” ERJ open research (2023). PMID: 36923566 ↗
L2OTHERCited in: 4. Clinical Presentation - [224]
D'Cruz RF, Waller MD, Perrin F et al.. “Chest radiography is a poor predictor of respiratory symptoms and functional impairment in survivors of severe COVID-19 pneumonia.” ERJ open research (2021). PMID: 33575312 ↗
L2OTHERCited in: 4. Clinical Presentation, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, 10. Complications - [225]
Migliori GB, Langendam MW, D'Ambrosio L et al.. “Protecting the tuberculosis drug pipeline: stating the case for the rational use of fluoroquinolones.” The European respiratory journal (2012). PMID: 22653774 ↗
L1SR_OBSCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [226]
Konstantinidis I, Jones BE, Ramirez J et al.. “Summary for Clinicians: Clinical Practice Guideline for the Diagnosis and Management of Community-acquired Pneumonia.” Annals of the American Thoracic Society (2026). PMID: 41902840 ↗
L1GUIDELINECited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [227]
Chalmers JD, Singanayagam A, Akram AR et al.. “Severity assessment tools for predicting mortality in hospitalised patients with community-acquired pneumonia. Systematic review and meta-analysis.” Thorax (2010). PMID: 20729231 ↗
L2SR_OBSCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 11. Prognosis and Natural History - [228]
Horita N, Miyazawa N, Kojima R et al.. “Sensitivity and specificity of the Streptococcus pneumoniae urinary antigen test for unconcentrated urine from adult patients with pneumonia: a meta-analysis.” Respirology (Carlton, Vic.) (2013). PMID: 23910720 ↗
L2SR_OBSCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [229]
Bhuiyan MU, Snelling TL, West R et al.. “The contribution of viruses and bacteria to community-acquired pneumonia in vaccinated children: a case-control study.” Thorax (2018). PMID: 30337417 ↗
L3CASE_CONTROLCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [230]
Obiora E, Hubbard R, Sanders RD et al.. “The impact of benzodiazepines on occurrence of pneumonia and mortality from pneumonia: a nested case-control and survival analysis in a population-based cohort.” Thorax (2012). PMID: 23220867 ↗
L3CASE_CONTROLCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 8. Long-term and Definitive Management - [231]
Scicluna BP, Klein Klouwenberg PM, van Vught LA et al.. “A molecular biomarker to diagnose community-acquired pneumonia on intensive care unit admission.” American journal of respiratory and critical care medicine (2015). PMID: 26121490 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 10. Complications - [232]
Sellares J, López-Giraldo A, Lucena C et al.. “Influence of previous use of inhaled corticoids on the development of pleural effusion in community-acquired pneumonia.” American journal of respiratory and critical care medicine (2013). PMID: 23590264 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 10. Complications - [233]
Ambrosino N, Guarracino F. “Unusual applications of noninvasive ventilation.” The European respiratory journal (2011). PMID: 21349915 ↗
L5REVIEW_NARRATIVECited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive), 10. Complications, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [234]
Singanayagam A, Chalmers JD, Akram AR et al.. “Impact of inhaled corticosteroid use on outcome in COPD patients admitted with pneumonia.” The European respiratory journal (2011). PMID: 21429980 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [235]
Camps Serra M, Cervera C, Pumarola T et al.. “Virological diagnosis in community-acquired pneumonia in immunocompromised patients.” The European respiratory journal (2007). PMID: 17959637 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 12. Special Populations & Pregnancy - [236]
Torres A, Cillóniz C, Ferrer M et al.. “Bacteraemia and antibiotic-resistant pathogens in community acquired pneumonia: risk and prognosis.” The European respiratory journal (2015). PMID: 25614173 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue - [237]
Capelastegui A, España PP, Quintana JM et al.. “Validation of a predictive rule for the management of community-acquired pneumonia.” The European respiratory journal (2006). PMID: 16387948 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [238]
Huijts SM, Pride MW, Vos JM et al.. “Diagnostic accuracy of a serotype-specific antigen test in community-acquired pneumonia.” The European respiratory journal (2013). PMID: 23397295 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [239]
Teepe J, Grigoryan L, Verheij TJ. “Determinants of community-acquired pneumonia in children and young adults in primary care.” The European respiratory journal (2010). PMID: 20436174 ↗
L3OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 12. Special Populations & Pregnancy - [240]
Mongodi S, Via G, Girard M et al.. “Lung Ultrasound for Early Diagnosis of Ventilator-Associated Pneumonia.” Chest (2015). PMID: 26836896 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [241]
Ceccato A, Torres A, Cilloniz C et al.. “Invasive Disease vs Urinary Antigen-Confirmed Pneumococcal Community-Acquired Pneumonia.” Chest (2017). PMID: 28093269 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 10. Complications - [242]
Donovan FM, Thompson GR, Blair JE et al.. “Managing Cavitary Coccidioidomycosis Expert Opinions for Improving Patient Outcomes.” Chest (2024). PMID: 39675520 ↗
L5REVIEW_NARRATIVECited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 8. Long-term and Definitive Management, 10. Complications - [243]
Joean O, von Eynern LP, Welte T et al.. “Clinical Features, Diagnostics, Etiology, and Outcomes of Hospitalized Solid Organ Recipients With Community-Acquired Pneumonia: A Retrospective Cohort Analysis.” Chest (2024). PMID: 38823578 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [244]
Thomas CP, Ryan M, Chapman JD et al.. “Incidence and cost of pneumonia in medicare beneficiaries.” Chest (2012). PMID: 22406959 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 8. Long-term and Definitive Management, 12. Special Populations & Pregnancy - [245]
Huang DT, Angus DC, Kellum JA et al.. “Midregional proadrenomedullin as a prognostic tool in community-acquired pneumonia.” Chest (2009). PMID: 19363212 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [246]
Menéndez R, Sahuquillo-Arce JM, Reyes S et al.. “Cytokine activation patterns and biomarkers are influenced by microorganisms in community-acquired pneumonia.” Chest (2011). PMID: 22194589 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [247]
Jennings LC, Anderson TP, Beynon KA et al.. “Incidence and characteristics of viral community-acquired pneumonia in adults.” Thorax (2007). PMID: 17573440 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [248]
Lahti E, Peltola V, Waris M et al.. “Induced sputum in the diagnosis of childhood community-acquired pneumonia.” Thorax (2008). PMID: 19052043 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [249]
Lim WS, Smith DL, Wise MP et al.. “British Thoracic Society community acquired pneumonia guideline and the NICE pneumonia guideline: how they fit together.” Thorax (2015). PMID: 25977290 ↗
L5OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [250]
Bewick T, Cooper VJ, Lim WS. “Does early review by a respiratory physician lead to a shorter length of stay for patients with non-severe community-acquired pneumonia?” Thorax (2009). PMID: 19386582 ↗
L2REVIEW_NARRATIVECited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue - [251]
Miyashita N, Akaike H, Teranishi H et al.. “Chest computed tomography for the diagnosis of Mycoplasma pneumoniae infection.” Respirology (Carlton, Vic.) (2013). PMID: 25219424 ↗
L4CASE_REPORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [252]
Das RR, Singh M, Naik SS. “Vitamin D as an adjunct to antibiotics for the treatment of acute childhood pneumonia.” The Cochrane database of systematic reviews (2018). PMID: 30024634 ↗
L1SR_OBSCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [253]
Samara KA, Barqawi HJ, Adra S et al.. “PneumoMLPred: Innovating pneumonia management with guideline adherence review and explainable machine learning-based mortality prediction - A single-centre retrospective study.” Respiratory medicine (2026). PMID: 42162923 ↗
L4COHORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [254]
. “Aspiration pneumonia.” Respirology (Carlton, Vic.) (2009). PMID: 19857224 ↗
L5OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [255]
Aston SJ. “Pneumonia in the developing world: Characteristic features and approach to management.” Respirology (Carlton, Vic.) (2017). PMID: 28681972 ↗
L5REVIEW_NARRATIVECited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [256]
Ferrer M, Torres A, Martínez R et al.. “Inhaled corticosteroids and systemic inflammatory response in community-acquired pneumonia: a prospective clinical study.” Respirology (Carlton, Vic.) (2014). PMID: 24909304 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management - [257]
Lui G, Ip M, Lee N et al.. “Role of 'atypical pathogens' among adult hospitalized patients with community-acquired pneumonia.” Respirology (Carlton, Vic.) (2009). PMID: 19818051 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue, 12. Special Populations & Pregnancy - [258]
Takazono T, Namie H, Nagayoshi Y et al.. “Development of a score model to predict long-term prognosis after community-onset pneumonia in older patients.” Respirology (Carlton, Vic.) (2024). PMID: 38769707 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 8. Long-term and Definitive Management, 12. Special Populations & Pregnancy - [259]
Molinos L, Zalacain R, Menéndez R et al.. “Sensitivity, Specificity, and Positivity Predictors of the Pneumococcal Urinary Antigen Test in Community-Acquired Pneumonia.” Annals of the American Thoracic Society (2015). PMID: 26288389 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [260]
Prins HJ, Duijkers R, Kramer G et al.. “Relationship between biomarkers and findings on low-dose computed tomography in hospitalised patients with acute exacerbation of COPD.” ERJ open research (2022). PMID: 35747233 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue - [261]
Dobler CC, Hakim M, Singh S et al.. “Ability of the LACE index to predict 30-day hospital readmissions in patients with community-acquired pneumonia.” ERJ open research (2020). PMID: 32714954 ↗
L4OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 7. Acute Management and Exacerbation Rescue - [262]
Daniel P, Rodrigo C, Bewick T et al.. “Increased incidence of adult pneumococcal pneumonia during school holiday periods.” ERJ open research (2017). PMID: 28326311 ↗
L2OTHERCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [263]
Yurt R, Agca M, Turkar A et al.. “Impact of emphysema on biomarkers in hospitalized COPD patients with community-acquired pneumonia: a retrospective study.” BMC pulmonary medicine (2026). PMID: 42177477 ↗
L4COHORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [264]
Zha Q, Li H, Li Y et al.. “Clinical characteristics of Mycoplasma pneumoniae pneumonia in children and construction of a severe case prediction model: a retrospective study from Yan'an, China.” Frontiers in pediatrics (2026). PMID: 41960034 ↗
L4COHORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [265]
Li G, Li X, Feng Q et al.. “A case report of spherical pneumonia caused by Chlamydia psittaci infection.” Frontiers in medicine (2026). PMID: 42338934 ↗
L4CASE_REPORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [266]
Zamfir AS, Mihailovici AS, Mihai F et al.. “Case Report: Chronic eosinophilic pneumonia with acute-like presentation and diagnostic challenges.” Frontiers in medicine (2026). PMID: 42318416 ↗
L4CASE_REPORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [267]
Li Q, Su G, Yu R et al.. “Application of BALF combined with tNGS for detecting Chlamydia psittaci in resource-limited areas: lessons learned from the 2025 temporally associated case series investigation.” BMC infectious diseases (2026). PMID: 42288822 ↗
L4CASE_REPORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored) - [268]
Pan J, Kong H, Liang M et al.. “Pneumonia caused by co-infection with Mycobacterium tuberculosis and Pneumocystis jirovecii leading to acute respiratory distress syndrome in an HIV-negative immunocompromised patient: a case report and literature review.” BMC infectious diseases (2026). PMID: 42026490 ↗
L4CASE_REPORTCited in: 5. Diagnosis and Workup (Pulmonary Function, Bronchoscopy and Imaging Anchored), 12. Special Populations & Pregnancy - [269]
Snijders D, Daniels JM, de Graaff CS et al.. “Efficacy of corticosteroids in community-acquired pneumonia: a randomized double-blinded clinical trial.” American journal of respiratory and critical care medicine (2010). PMID: 20133929 ↗
L1RCTCited in: 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [270]
Christ-Crain M, Stolz D, Bingisser R et al.. “Procalcitonin guidance of antibiotic therapy in community-acquired pneumonia: a randomized trial.” American journal of respiratory and critical care medicine (2006). PMID: 16603606 ↗
L1RCTCited in: 6. Severity, Staging and Risk Stratification, 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [271]
Arnold FW, Summersgill JT, Lajoie AS et al.. “A worldwide perspective of atypical pathogens in community-acquired pneumonia.” American journal of respiratory and critical care medicine (2007). PMID: 17332485 ↗
L5OTHERCited in: 6. Severity, Staging and Risk Stratification - [272]
Chouchane O, Michels EHA, Leite GGF et al.. “The proteomic landscape of blood monocytes in community-acquired pneumonia.” The European respiratory journal (2025). PMID: 41151990 ↗
L3OTHERCited in: 6. Severity, Staging and Risk Stratification, History and Evolution of Treatment - [273]
Bastrup Israelsen S, Fally M, Brok Nielsen P et al.. “Reassessing Halm's clinical stability criteria in community-acquired pneumonia management.” The European respiratory journal (2024). PMID: 39174283 ↗
L4OTHERCited in: 6. Severity, Staging and Risk Stratification, 10. Complications, 12. Special Populations & Pregnancy - [274]
Niederman MS. “Recent advances in community-acquired pneumonia: inpatient and outpatient.” Chest (2007). PMID: 17426229 ↗
L5REVIEW_NARRATIVECited in: 6. Severity, Staging and Risk Stratification, History and Evolution of Treatment, 11. Prognosis and Natural History - [275]
Deshpande A, Klompas M, Yu PC et al.. “Influenza Testing and Treatment Among Patients Hospitalized With Community-Acquired Pneumonia.” Chest (2022). PMID: 35134384 ↗
L4OTHERCited in: 6. Severity, Staging and Risk Stratification, 11. Prognosis and Natural History - [276]
Waterer GW, Self WH, Courtney DM et al.. “In-Hospital Deaths Among Adults With Community-Acquired Pneumonia.” Chest (2018). PMID: 29859184 ↗
L4OTHERCited in: 6. Severity, Staging and Risk Stratification - [277]
Lim WS. “Severity assessment in community-acquired pneumonia: moving on.” Thorax (2007). PMID: 17387212 ↗
L5OTHERCited in: 6. Severity, Staging and Risk Stratification - [278]
Li Y, Zhu H, Li G et al.. “Computed tomography findings and severity scores in Chlamydia psittaci pneumonia: a retrospective study of 69 cases with clinical correlation.” BMC infectious diseases (2026). PMID: 42365231 ↗
L2COHORTCited in: 6. Severity, Staging and Risk Stratification - [279]
Ceccato A, Mendez R, Ewig S et al.. “Validation of a Prediction Score for Drug-Resistant Microorganisms in Community-acquired Pneumonia.” Annals of the American Thoracic Society (2021). PMID: 32915057 ↗
L2OTHERCited in: 6. Severity, Staging and Risk Stratification - [280]
Sapey E, Patel JM, Greenwood H et al.. “Simvastatin Improves Neutrophil Function and Clinical Outcomes in Pneumonia. A Pilot Randomized Controlled Clinical Trial.” American journal of respiratory and critical care medicine (2019). PMID: 31206313 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History, 12. Special Populations & Pregnancy - [281]
Sapey E, Patel JM, Greenwood HL et al.. “Pulmonary Infections in the Elderly Lead to Impaired Neutrophil Targeting, Which Is Improved by Simvastatin.” American journal of respiratory and critical care medicine (2017). PMID: 28657793 ↗
L4RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 12. Special Populations & Pregnancy - [282]
Lorgelly PK, Atkinson M, Lakhanpaul M et al.. “Oral versus i.v. antibiotics for community-acquired pneumonia in children: a cost-minimisation analysis.” The European respiratory journal (2009). PMID: 19717479 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [283]
Wu X, Sun T, He H et al.. “Effect of Metagenomic Next-Generation Sequencing on Clinical Outcomes of Patients With Severe Community-Acquired Pneumonia in the ICU: A Multicenter, Randomized Controlled Trial.” Chest (2024). PMID: 39067508 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 11. Prognosis and Natural History - [284]
El Moussaoui R, Opmeer BC, de Borgie CA et al.. “Long-term symptom recovery and health-related quality of life in patients with mild-to-moderate-severe community-acquired pneumonia.” Chest (2006). PMID: 17035452 ↗
L2RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management - [285]
Cosentini R, Brambilla AM, Aliberti S et al.. “Helmet continuous positive airway pressure vs oxygen therapy to improve oxygenation in community-acquired pneumonia: a randomized, controlled trial.” Chest (2010). PMID: 20154071 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management - [286]
Bonten MJ, Huijts SM, Bolkenbaas M et al.. “Polysaccharide conjugate vaccine against pneumococcal pneumonia in adults.” The New England journal of medicine (2015). PMID: 25785969 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [287]
Reijnders TDY, Laterre PF, François B et al.. “Effect of mesenchymal stem cells on the host response in severe community-acquired pneumonia.” Thorax (2024). PMID: 39322407 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [288]
Alfageme I, Vazquez R, Reyes N et al.. “Clinical efficacy of anti-pneumococcal vaccination in patients with COPD.” Thorax (2005). PMID: 16227328 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 13. Prevention, Screening & Surveillance - [289]
Falguera M, Ruiz-González A, Schoenenberger JA et al.. “Prospective, randomised study to compare empirical treatment versus targeted treatment on the basis of the urine antigen results in hospitalised patients with community-acquired pneumonia.” Thorax (2009). PMID: 19703825 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [290]
Müller F, Christ-Crain M, Bregenzer T et al.. “Procalcitonin levels predict bacteremia in patients with community-acquired pneumonia: a prospective cohort trial.” Chest (2010). PMID: 20299634 ↗
L2TRIAL_NONRANDOMCited in: 7. Acute Management and Exacerbation Rescue - [291]
Long W, Deng X, Zhang Y et al.. “Procalcitonin guidance for reduction of antibiotic use in low-risk outpatients with community-acquired pneumonia.” Respirology (Carlton, Vic.) (2011). PMID: 21507143 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [292]
Fox SC, Trivedi AP. “A 47-Year Old Woman With Rapidly Progressive Hypoxemic Respiratory Failure.” Chest (2021). PMID: 33563457 ↗
L4CASE_REPORTCited in: 7. Acute Management and Exacerbation Rescue, 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive), 10. Complications - [293]
Adamuz J, Viasus D, Campreciós-Rodríguez P et al.. “A prospective cohort study of healthcare visits and rehospitalizations after discharge of patients with community-acquired pneumonia.” Respirology (Carlton, Vic.) (2011). PMID: 21736665 ↗
L2COHORTCited in: 7. Acute Management and Exacerbation Rescue - [294]
Cillóniz C, Ewig S, Polverino E et al.. “Community-acquired pneumonia in outpatients: aetiology and outcomes.” The European respiratory journal (2012). PMID: 22267760 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue, 10. Complications - [295]
Tagami T, Matsui H, Horiguchi H et al.. “Low-dose corticosteroid use and mortality in severe community-acquired pneumonia patients.” The European respiratory journal (2014). PMID: 25323232 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue - [296]
Endeman H, Meijvis SC, Rijkers GT et al.. “Systemic cytokine response in patients with community-acquired pneumonia.” The European respiratory journal (2010). PMID: 20884746 ↗
L4OTHERCited in: 7. Acute Management and Exacerbation Rescue - [297]
Ewig S, Torres A. “Community-acquired pneumonia as an emergency: time for an aggressive intervention to lower mortality.” The European respiratory journal (2011). PMID: 21349916 ↗
L5OTHERCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management - [298]
Cao B, Huang GH, Pu ZH et al.. “Emergence of community-acquired adenovirus type 55 as a cause of community-onset pneumonia.” Chest (2014). PMID: 24551881 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue, 13. Prevention, Screening & Surveillance - [299]
Crisafulli E, Menéndez R, Huerta A et al.. “Systemic inflammatory pattern of patients with community-acquired pneumonia with and without COPD.” Chest (2013). PMID: 23187314 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue - [300]
Hashmi M, Haniffa R, Jayakumar D et al.. “Ivermectin for Critically and Noncritically Ill Hospitalized Patients With COVID-19: Randomized, Embedded, Multifactorial Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP).” Critical care medicine (2026). PMID: 42101205 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [301]
Elmeazawy R, AbdElsamea MZ, Barakat A et al.. “Oral pentoxifylline as a novel adjunct to standard therapy in pediatric community-acquired pneumonia: a randomized controlled trial.” Pediatric research (2026). PMID: 42086944 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 12. Special Populations & Pregnancy - [302]
Hsiao A, Leong T, Fireman B et al.. “Adjuvanted vs High-Dose Influenza Vaccines in Older US Adults: A Cluster Randomized Crossover Study.” JAMA network open (2026). PMID: 42081247 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 13. Prevention, Screening & Surveillance - [303]
Stylianakis E, Kakavoulis N, Foutadakis S et al.. “Molecular pathways driving clarithromycin benefit in community-acquired pneumonia: analysis of the ACCESS randomised trial.” EBioMedicine (2026). PMID: 41934919 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment, 10. Complications - [304]
Bradbury CA, McVerry BJ, Lawler PR et al.. “Intermediate dose heparin thromboprophylaxis among critically ill patients with COVID-19: a randomized clinical trial.” Journal of thrombosis and haemostasis : JTH (2026). PMID: 41895526 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [305]
Pinot J, Delory T, Pétrier M et al.. “Clinical data, chest X-ray or C-reactive protein to initiate antibiotic therapy in outpatients with suspected community-acquired pneumonia: a prospective, randomized, controlled, digital case vignette study.” Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases (2026). PMID: 41839418 ↗
L4RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [306]
Baghdadi JD, Harris AD, Pineles L et al.. “Using Probability of Community-Acquired Pneumonia to Tailor Antimicrobials Among Inpatients: A Pragmatic, Randomized Trial.” Clinical infectious diseases : an official publication of the Infectious Diseases Society of America (2026). PMID: 41823187 ↗
L1RCTCited in: 7. Acute Management and Exacerbation Rescue, 8. Long-term and Definitive Management, History and Evolution of Treatment - [307]
Menéndez R, Martinez R, Reyes S et al.. “Stability in community-acquired pneumonia: one step forward with markers?” Thorax (2009). PMID: 19762338 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue, 10. Complications - [308]
Phua J, See KC, Chan YH et al.. “Validation and clinical implications of the IDSA/ATS minor criteria for severe community-acquired pneumonia.” Thorax (2009). PMID: 19386583 ↗
L3OTHERCited in: 7. Acute Management and Exacerbation Rescue - [309]
Man SY, Lee N, Ip M et al.. “Prospective comparison of three predictive rules for assessing severity of community-acquired pneumonia in Hong Kong.” Thorax (2006). PMID: 17121867 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue - [310]
Stotts C, Corrales-Medina VF, deKemp RA et al.. “Targeting Vascular Inflammation In Patients with Community-Acquired Pneumonia (TIN-CAP): protocol for a multicentre, randomised, double-blind, placebo-controlled trial.” BMJ open (2026). PMID: 41781043 ↗
L5TRIAL_NONRANDOMCited in: 7. Acute Management and Exacerbation Rescue, 10. Complications - [311]
Lansbury L, Rodrigo C, Leonardi-Bee J et al.. “Corticosteroids as adjunctive therapy in the treatment of influenza.” The Cochrane database of systematic reviews (2019). PMID: 30798570 ↗
L1SR_OBSCited in: 7. Acute Management and Exacerbation Rescue - [312]
Serisier DJ, Williams S, Bowler SD. “Australasian respiratory and emergency physicians do not use the pneumonia severity index in community-acquired pneumonia.” Respirology (Carlton, Vic.) (2013). PMID: 23036136 ↗
L4OTHERCited in: 7. Acute Management and Exacerbation Rescue - [313]
Tseng JS, Chan MC, Hsu JY et al.. “Procalcitonin is a valuable prognostic marker in ARDS caused by community-acquired pneumonia.” Respirology (Carlton, Vic.) (2008). PMID: 18422867 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue, 10. Complications - [314]
Serisier DJ, Bowler SD. “Effect of a simple educational intervention on the hospital management of community-acquired pneumonia.” Respirology (Carlton, Vic.) (2007). PMID: 17539843 ↗
L4OTHERCited in: 7. Acute Management and Exacerbation Rescue - [315]
Chang CL, Sullivan GD, Karalus NC et al.. “Predicting early mortality in acute exacerbation of chronic obstructive pulmonary disease using the CURB65 score.” Respirology (Carlton, Vic.) (2011). PMID: 20920140 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue - [316]
Kim RY, Glick C, Furmanek S et al.. “Association between body mass index and mortality in hospitalised patients with community-acquired pneumonia.” ERJ open research (2021). PMID: 33778059 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue - [317]
Venkitakrishnan R, Vijay A, Augustine J et al.. “Hospitalisation outcomes in pneumococcal-vaccinated versus -unvaccinated patients with exacerbation of COPD: results from the HOPE COPD Study.” ERJ open research (2023). PMID: 37143841 ↗
L2OTHERCited in: 7. Acute Management and Exacerbation Rescue, 13. Prevention, Screening & Surveillance - [318]
Wittermans E, Vestjens SMT, Spoorenberg SMC et al.. “Adjunctive treatment with oral dexamethasone in non-ICU patients hospitalised with community-acquired pneumonia: a randomised clinical trial.” The European respiratory journal (2021). PMID: 33446608 ↗
L1RCTCited in: 8. Long-term and Definitive Management - [319]
Ebrahimi F, Wolffenbuttel C, Blum CA et al.. “Fibroblast growth factor 21 predicts outcome in community-acquired pneumonia: secondary analysis of two randomised controlled trials.” The European respiratory journal (2019). PMID: 30578395 ↗
L2RCTCited in: 8. Long-term and Definitive Management, History and Evolution of Treatment - [320]
Ebrahimi F, Giaglis S, Hahn S et al.. “Markers of neutrophil extracellular traps predict adverse outcome in community-acquired pneumonia: secondary analysis of a randomised controlled trial.” The European respiratory journal (2018). PMID: 29519921 ↗
L2RCTCited in: 8. Long-term and Definitive Management - [321]
Neupane B, Jerrett M, Burnett RT et al.. “Long-term exposure to ambient air pollution and risk of hospitalization with community-acquired pneumonia in older adults.” American journal of respiratory and critical care medicine (2009). PMID: 19797763 ↗
L3OTHERCited in: 8. Long-term and Definitive Management, 12. Special Populations & Pregnancy - [322]
Krüger S, Ewig S, Giersdorf S et al.. “Cardiovascular and inflammatory biomarkers to predict short- and long-term survival in community-acquired pneumonia: Results from the German Competence Network, CAPNETZ.” American journal of respiratory and critical care medicine (2010). PMID: 20639437 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [323]
van der Sande LJTM, Jöbsis Q, Bannier MAGE et al.. “The risk of community-acquired pneumonia in children using gastric acid suppressants.” The European respiratory journal (2021). PMID: 33737412 ↗
L3OTHERCited in: 8. Long-term and Definitive Management, 10. Complications - [324]
Almirall J, Bolíbar I, Serra-Prat M et al.. “Inhaled drugs as risk factors for community-acquired pneumonia.” The European respiratory journal (2010). PMID: 20525710 ↗
L3OTHERCited in: 8. Long-term and Definitive Management - [325]
Guertler C, Wirz B, Christ-Crain M et al.. “Inflammatory responses predict long-term mortality risk in community-acquired pneumonia.” The European respiratory journal (2010). PMID: 21071473 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [326]
Bello S, Lasierra AB, Mincholé E et al.. “Prognostic power of proadrenomedullin in community-acquired pneumonia is independent of aetiology.” The European respiratory journal (2011). PMID: 22075489 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [327]
Tessmer A, Welte T, Schmidt-Ott R et al.. “Influenza vaccination is associated with reduced severity of community-acquired pneumonia.” The European respiratory journal (2010). PMID: 21148226 ↗
L2OTHERCited in: 8. Long-term and Definitive Management, 13. Prevention, Screening & Surveillance - [328]
Siljan WW, Holter JC, Michelsen AE et al.. “Inflammatory biomarkers are associated with aetiology and predict outcomes in community-acquired pneumonia: results of a 5-year follow-up cohort study.” ERJ open research (2019). PMID: 30863773 ↗
L2COHORTCited in: 8. Long-term and Definitive Management - [329]
Menéndez R, Méndez R, Aldás I et al.. “Community-Acquired Pneumonia Patients at Risk for Early and Long-term Cardiovascular Events Are Identified by Cardiac Biomarkers.” Chest (2019). PMID: 31381883 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [330]
Corrales-Medina VF, van Walraven C. “Guideline-Concordant Antibiotic Therapy for the Hospital Treatment of Community-Acquired Pneumonia and 1-Year All-Cause and Cardiovascular Mortality in Older Adult Patients Surviving to Discharge.” Chest (2023). PMID: 36621760 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [331]
Suissa S, Dell'Aniello S, Ernst P. “Long-Acting Bronchodilator Initiation in COPD and the Risk of Adverse Cardiopulmonary Events: A Population-Based Comparative Safety Study.” Chest (2016). PMID: 27554300 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [332]
Voiriot G, Dury S, Parrot A et al.. “Nonsteroidal antiinflammatory drugs may affect the presentation and course of community-acquired pneumonia.” Chest (2010). PMID: 20724739 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [333]
Nowak A, Breidthardt T, Christ-Crain M et al.. “Direct comparison of three natriuretic peptides for prediction of short- and long-term mortality in patients with community-acquired pneumonia.” Chest (2011). PMID: 22135381 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [334]
Saghaug CS, Markussen DL, Knoop ST et al.. “Diagnostic accuracy of a host response test in suspected community-Acquired pneumonia during the COVID-19 era.” International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases (2025). PMID: 40907740 ↗
L2RCTCited in: 8. Long-term and Definitive Management - [335]
Cheon K, Buchwald UK, Hammitt LL et al.. “The impact of pneumococcal vaccination and nasopharyngeal colonization on the performance of a serotype-specific urine antigen detection (SSUAD) assay.” Vaccine (2025). PMID: 40886427 ↗
L1RCTCited in: 8. Long-term and Definitive Management - [336]
Krüger S, Ewig S, Kunde J et al.. “Pro-atrial natriuretic peptide and pro-vasopressin for predicting short-term and long-term survival in community-acquired pneumonia: results from the German Competence Network CAPNETZ.” Thorax (2010). PMID: 20335288 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [337]
Yu M, Wang X, Wu S et al.. “Comparison of Efficacy and Safety Profiles Between Omadacycline and Moxifloxacin in Elderly Patients with Community-Acquired Pneumonia: A Randomized, Controlled Trial.” Clinical pharmacology in drug development (2025). PMID: 41267642 ↗
L1RCTCited in: 8. Long-term and Definitive Management, History and Evolution of Treatment - [338]
Spoorenberg SM, Vestjens SM, Rijkers GT et al.. “YKL-40, CCL18 and SP-D predict mortality in patients hospitalized with community-acquired pneumonia.” Respirology (Carlton, Vic.) (2016). PMID: 27782361 ↗
L2OTHERCited in: 8. Long-term and Definitive Management - [339]
Bernstein JM. “Treatment of community-acquired pneumonia--IDSA guidelines. Infectious Diseases Society of America.” Chest (1999). PMID: 10084453 ↗
L1GUIDELINECited in: History and Evolution of Treatment - [340]
Ramsdell J, Narsavage GL, Fink JB. “Management of community-acquired pneumonia in the home: an American College of Chest Physicians clinical position statement.” Chest (2005). PMID: 15888856 ↗
L1GUIDELINECited in: History and Evolution of Treatment - [341]
Confalonieri M, Urbino R, Potena A et al.. “Hydrocortisone infusion for severe community-acquired pneumonia: a preliminary randomized study.” American journal of respiratory and critical care medicine (2004). PMID: 15557131 ↗
L1RCTCited in: History and Evolution of Treatment - [342]
Confalonieri M, Potena A, Carbone G et al.. “Acute respiratory failure in patients with severe community-acquired pneumonia. A prospective randomized evaluation of noninvasive ventilation.” American journal of respiratory and critical care medicine (1999). PMID: 10556125 ↗
L1RCTCited in: History and Evolution of Treatment - [343]
Lode H, Garau J, Grassi C et al.. “Treatment of community-acquired pneumonia: a randomized comparison of sparfloxacin, amoxycillin-clavulanic acid and erythromycin.” The European respiratory journal (1995). PMID: 8666093 ↗
L1RCTCited in: History and Evolution of Treatment - [344]
Wasserfallen JB, Erard V, Cometta A et al.. “Cost-effectiveness of full-course oral levofloxacin in severe community-acquired pneumonia.” The European respiratory journal (2004). PMID: 15459145 ↗
L1RCTCited in: History and Evolution of Treatment - [345]
Torres A, Muir JF, Corris P et al.. “Effectiveness of oral moxifloxacin in standard first-line therapy in community-acquired pneumonia.” The European respiratory journal (2003). PMID: 12570122 ↗
L1RCTCited in: History and Evolution of Treatment - [346]
Mundy LM, Leet TL, Darst K et al.. “Early mobilization of patients hospitalized with community-acquired pneumonia.” Chest (2003). PMID: 12970012 ↗
L1RCTCited in: History and Evolution of Treatment - [347]
El Moussaoui R, Opmeer BC, Bossuyt PM et al.. “Development and validation of a short questionnaire in community acquired pneumonia.” Thorax (2004). PMID: 15223867 ↗
L4RCTCited in: History and Evolution of Treatment - [348]
Blasi F. “Atypical pathogens and respiratory tract infections.” The European respiratory journal (2004). PMID: 15293621 ↗
L5REVIEW_NARRATIVECited in: History and Evolution of Treatment - [349]
Almirall J, Bolíbar I, Balanzó X et al.. “Risk factors for community-acquired pneumonia in adults: a population-based case-control study.” The European respiratory journal (1999). PMID: 10065680 ↗
L3CASE_CONTROLCited in: History and Evolution of Treatment - [350]
Soepandi P, Mangunnegoro H, Yunus F et al.. “The pattern of micro-organisms and the efficacy of new macrolide in acute lower respiratory tract infections.” Respirology (Carlton, Vic.) (1998). PMID: 9692520 ↗
L4RCTCited in: History and Evolution of Treatment - [351]
Zalacain R, Torres A, Celis R et al.. “Community-acquired pneumonia in the elderly: Spanish multicentre study.” The European respiratory journal (2003). PMID: 12608444 ↗
L2OTHERCited in: History and Evolution of Treatment - [352]
Lynn LA. “Flawed design and selection bias in critical care randomized controlled trials (RCTs): the patient safety risk of the "RCT mimic".” Patient safety in surgery (2025). PMID: 41402862 ↗
L5RCTCited in: History and Evolution of Treatment - [353]
Sperandeo M, Rea G, Grimaldi MA et al.. “Contrast-enhanced ultrasound does not discriminate between community acquired pneumonia and lung cancer.” Thorax (2016). PMID: 27742872 ↗
L3OTHERCited in: History and Evolution of Treatment - [354]
Neill AM, Martin IR, Weir R et al.. “Community acquired pneumonia: aetiology and usefulness of severity criteria on admission.” Thorax (1996). PMID: 8977602 ↗
L2OTHERCited in: History and Evolution of Treatment - [355]
Rodrigo C, Bewick T, Sheppard C et al.. “Pneumococcal serotypes in adult non-invasive and invasive pneumonia in relation to child contact and child vaccination status.” Thorax (2013). PMID: 24048505 ↗
L2OTHERCited in: History and Evolution of Treatment, 13. Prevention, Screening & Surveillance - [356]
Okimoto N, Asaoka N, Osaki K et al.. “Clinical features of Q fever pneumonia.” Respirology (Carlton, Vic.) (2004). PMID: 15182283 ↗
L4CASE_REPORTCited in: History and Evolution of Treatment - [357]
Isenman HL, Chambers ST, Pithie AD et al.. “Legionnaires' disease caused by Legionella longbeachae: Clinical features and outcomes of 107 cases from an endemic area.” Respirology (Carlton, Vic.) (2016). PMID: 27199169 ↗
L4OTHERCited in: History and Evolution of Treatment - [358]
St Peter SD, Ampofo K, Brogan T et al.. “2026 Clinical Practice Guideline Update by the Infectious Diseases Society of America and the Pediatric Infectious Diseases Society on The Management of Community-acquired Pneumonia in Infants and Children Older than 3 Months of Age: The Choice of Chest Tube Size.” Clinical infectious diseases : an official publication of the Infectious Diseases Society of America (2026). PMID: 41840880 ↗
L1GUIDELINECited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [359]
St Peter SD, Ampofo K, Brogan T et al.. “2026 Clinical Practice Guideline Update by the Infectious Diseases Society of America and the Pediatric Infectious Diseases Society on The Management of Community-Acquired Pneumonia in Infants and Children Older than 3 Months of Age: The Use of Pleural fluid drainage compared to Surgical Debridement.” Clinical infectious diseases : an official publication of the Infectious Diseases Society of America (2026). PMID: 41834669 ↗
L1GUIDELINECited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [360]
Azar MM, Schlaberg R, Malinis MF et al.. “Added Diagnostic Utility of Clinical Metagenomics for the Diagnosis of Pneumonia in Immunocompromised Adults.” Chest (2020). PMID: 33217418 ↗
L2OTHERCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [361]
Schwartz B, Dupont V, Dury S et al.. “Aetiology, clinical features, diagnostic studies, and outcomes of community-acquired pneumonia in kidney transplant recipients admitted to hospital: a multicentre retrospective French cohort study.” Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases (2022). PMID: 36574948 ↗
L2COHORTCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [362]
Kim J, Park JS, Cho YJ et al.. “Predictors of prolonged stay in patients with community-acquired pneumonia and complicated parapneumonic effusion.” Respirology (Carlton, Vic.) (2015). PMID: 26510382 ↗
L2OTHERCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [363]
Hong Y, Wang Q, Song Y et al.. “Factors Associated with Severe Adenovirus Pneumonia in Children: A Retrospective Study from Guangzhou, China (2017-2019).” Medical science monitor : international medical journal of experimental and clinical research (2023). PMID: 37496263 ↗
L2COHORTCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [364]
Luo H, Jiang L, Chen J et al.. “Chlamydia psittaci Pneumonia in a patient with motor neuron disease: a case report.” BMC infectious diseases (2023). PMID: 38053032 ↗
L4CASE_REPORTCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [365]
Li Y, Lei J, Ren Z et al.. “Case Report: Metagenomic next-generation sequencing assists in dynamic pathogen monitoring: powerful tool for progressing severe pneumonia.” Frontiers in cellular and infection microbiology (2023). PMID: 37743869 ↗
L4CASE_REPORTCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [366]
Luo Y, Zhu L, Xu H et al.. “Landscape of the upper and lower airway microbiota in children with community-acquired pneumonia.” Virulence (2026). PMID: 42388029 ↗
L2OTHERCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [367]
Qian J, Liu M, Zhu C et al.. “Epidemiological shifts and clinical characteristics of childhood Chlamydia pneumoniae pneumonia in Beijing before, during, and after public health interventions (2017-2025).” BMC infectious diseases (2026). PMID: 42298460 ↗
L2OTHERCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [368]
Feng X, Du M, Feng S et al.. “Targeted next-generation sequencing for microbial and clinical diagnosis: a prospective controlled comparison between sputum and bronchoalveolar lavage fluid in patients with community-acquired pneumonia.” BMC infectious diseases (2026). PMID: 42177424 ↗
L2OTHERCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [369]
Qian Q, Jinghua S, Jiani W et al.. “A retrospective analysis of 266 cases: clinical features of Chlamydia pneumoniae pneumonia in children.” BMC infectious diseases (2026). PMID: 41933307 ↗
L4OTHERCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [370]
Hountras P, Cajigas H. “A 62-Year-Old Woman With Wheezing, Respiratory Failure, and an Abnormal CT Scan.” Chest (2017). PMID: 28889900 ↗
L4CASE_REPORTCited in: 10. Complications - [371]
Reyes S, Martinez R, Vallés JM et al.. “Determinants of hospital costs in community-acquired pneumonia.” The European respiratory journal (2008). PMID: 18448502 ↗
L2OTHERCited in: 10. Complications - [372]
de Wit M, Jones DG, Sessler CN et al.. “Alcohol-use disorders in the critically ill patient.” Chest (2010). PMID: 20923804 ↗
L5REVIEW_NARRATIVECited in: 10. Complications - [373]
Ali AS, Sheikh D, Chandler TR et al.. “Cardiovascular Complications Are the Primary Drivers of Mortality in Hospitalized Patients With SARS-CoV-2 Community-Acquired Pneumonia.” Chest (2022). PMID: 36410493 ↗
L2OTHERCited in: 10. Complications - [374]
Chen JH, Chang SS, Liu JJ et al.. “Comparison of clinical characteristics and performance of pneumonia severity score and CURB-65 among younger adults, elderly and very old subjects.” Thorax (2010). PMID: 20965934 ↗
L2OTHERCited in: 10. Complications, 12. Special Populations & Pregnancy - [375]
Zeng H, Yang C, Jiang M et al.. “Predicting length of hospital stay in community-acquired pneumonia using clinical and treatment factors: a retrospective study with restricted cubic spline and piecewise regression analysis.” Frontiers in public health (2026). PMID: 42100535 ↗
L2COHORTCited in: 10. Complications - [376]
Chen H, Fan Y, Zhang X et al.. “Nonlinear age-season dynamics and macrolide resistance of Mycoplasma pneumoniae: a large pediatric cohort study during the post-pandemic resurgence.” BMC infectious diseases (2026). PMID: 42021202 ↗
L2COHORTCited in: 10. Complications, 12. Special Populations & Pregnancy - [377]
Restrepo MI, Reyes LF. “Pneumonia as a cardiovascular disease.” Respirology (Carlton, Vic.) (2018). PMID: 29325222 ↗
L5REVIEW_NARRATIVECited in: 10. Complications - [378]
Shindo Y, Sato S, Maruyama E et al.. “Comparison of severity scoring systems A-DROP and CURB-65 for community-acquired pneumonia.” Respirology (Carlton, Vic.) (2008). PMID: 18713094 ↗
L4OTHERCited in: 10. Complications - [379]
Chien JY, Hsueh PR, Cheng WC et al.. “Temporal changes in cytokine/chemokine profiles and pulmonary involvement in severe acute respiratory syndrome.” Respirology (Carlton, Vic.) (2006). PMID: 17052299 ↗
L3OTHERCited in: 10. Complications - [380]
Chiang WC, Teoh OH, Chong CY et al.. “Epidemiology, clinical characteristics and antimicrobial resistance patterns of community-acquired pneumonia in 1702 hospitalized children in Singapore.” Respirology (Carlton, Vic.) (2007). PMID: 17298459 ↗
L4OTHERCited in: 10. Complications - [381]
Kasamatsu Y, Yamaguchi T, Kawaguchi T et al.. “Usefulness of a semi-quantitative procalcitonin test and the A-DROP Japanese prognostic scale for predicting mortality among adults hospitalized with community-acquired pneumonia.” Respirology (Carlton, Vic.) (2012). PMID: 22059525 ↗
L2OTHERCited in: 10. Complications - [382]
Torén K, Blanc PD, Qvarfordt I et al.. “Inhaled Corticosteroids Use and Risk of Invasive Pneumococcal Disease in a Population-based Study.” Annals of the American Thoracic Society (2020). PMID: 32649216 ↗
L3OTHERCited in: 10. Complications - [383]
Abdoli E, Eini P, Farashi S et al.. “Optimizing Intubation Prediction in Pneumonia Patients: A Systematic Review and Meta-Analysis of Machine Learning Algorithms.” Pulmonary medicine (2026). PMID: 41848079 ↗
L1SR_OBSCited in: 10. Complications - [384]
Jutant EM, Voiriot G, Labbé V et al.. “Endothelial dysfunction and hypercoagulability in severe sickle-cell acute chest syndrome.” ERJ open research (2021). PMID: 34912886 ↗
L2OTHERCited in: 10. Complications - [385]
Aliberti S, Ramirez J, Cosentini R et al.. “Acute myocardial infarction versus other cardiovascular events in community-acquired pneumonia.” ERJ open research (2015). PMID: 27730139 ↗
L2OTHERCited in: 10. Complications - [386]
Ito A, Ishida T, Tachibana H et al.. “Serial procalcitonin levels for predicting prognosis in community-acquired pneumonia.” Respirology (Carlton, Vic.) (2016). PMID: 27398948 ↗
L2OTHERCited in: 11. Prognosis and Natural History - [387]
Luna CM, Palma I, Niederman MS et al.. “The Impact of Age and Comorbidities on the Mortality of Patients of Different Age Groups Admitted with Community-acquired Pneumonia.” Annals of the American Thoracic Society (2016). PMID: 27398827 ↗
L2OTHERCited in: 11. Prognosis and Natural History - [388]
Long MB, Abo-Leyah H, Giam YH et al.. “SFX-01 in hospitalised patients with community-acquired pneumonia during the COVID-19 pandemic: a double-blind, randomised, placebo-controlled trial.” ERJ open research (2024). PMID: 38469377 ↗
L1OTHERCited in: 11. Prognosis and Natural History - [389]
Maruyama T, Fujisawa T, Suga S et al.. “Outcomes and Prognostic Features of Patients With Influenza Requiring Hospitalization and Receiving Early Antiviral Therapy: A Prospective Multicenter Cohort Study.” Chest (2016). PMID: 26203671 ↗
L2COHORTCited in: 12. Special Populations & Pregnancy - [390]
Yende S, Angus DC, Ding J et al.. “4G/5G plasminogen activator inhibitor-1 polymorphisms and haplotypes are associated with pneumonia.” American journal of respiratory and critical care medicine (2007). PMID: 17761618 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [391]
Carrabba M, Zarantonello M, Bonara P et al.. “Severity assessment of healthcare-associated pneumonia and pneumonia in immunosuppression.” The European respiratory journal (2012). PMID: 22408203 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [392]
Kothe H, Bauer T, Marre R et al.. “Outcome of community-acquired pneumonia: influence of age, residence status and antimicrobial treatment.” The European respiratory journal (2008). PMID: 18287129 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [393]
Zhou F, Wang Y, Liu Y et al.. “Disease severity and clinical outcomes of community-acquired pneumonia caused by non-influenza respiratory viruses in adults: a multicentre prospective registry study from the CAP-China Network.” The European respiratory journal (2019). PMID: 31164430 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [394]
Ramirez JA, Musher DM, Evans SE et al.. “Treatment of Community-Acquired Pneumonia in Immunocompromised Adults: A Consensus Statement Regarding Initial Strategies.” Chest (2020). PMID: 32561442 ↗
L5REVIEW_NARRATIVECited in: 12. Special Populations & Pregnancy - [395]
Cillóniz C, Polverino E, Ewig S et al.. “Impact of age and comorbidity on cause and outcome in community-acquired pneumonia.” Chest (2013). PMID: 23670047 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [396]
Díaz A, Barria P, Niederman M et al.. “Etiology of community-acquired pneumonia in hospitalized patients in chile: the increasing prevalence of respiratory viruses among classic pathogens.” Chest (2007). PMID: 17356093 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [397]
Arancibia F, Cortes CP, Valdés M et al.. “Importance of Legionella pneumophila in the etiology of severe community-acquired pneumonia in Santiago, Chile.” Chest (2014). PMID: 23764871 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [398]
Ewig S, Birkner N, Strauss R et al.. “New perspectives on community-acquired pneumonia in 388 406 patients. Results from a nationwide mandatory performance measurement programme in healthcare quality.” Thorax (2009). PMID: 19454409 ↗
L2OTHERCited in: 12. Special Populations & Pregnancy - [399]
Hemilä H, Louhiala P. “Vitamin C for preventing and treating pneumonia.” The Cochrane database of systematic reviews (2013). PMID: 23925826 ↗
L1SR_OBSCited in: 12. Special Populations & Pregnancy - [400]
Toba A, Yamazaki M, Mochizuki H et al.. “Lower incidence of acute respiratory distress syndrome in community-acquired pneumonia patients aged 85 years or older.” Respirology (Carlton, Vic.) (2010). PMID: 20070586 ↗
L4OTHERCited in: 12. Special Populations & Pregnancy - [401]
Lv Q, Li L, Wang R et al.. “Antiviral Efficacy of the Traditional Chinese Medicine Mixture Yuanzhixingrenheji Against Human Adenovirus-7 In Vitro, In Vivo, and in a Clinical Retrospective Study.” Pathogens (Basel, Switzerland) (2026). PMID: 42198590 ↗
L4COHORTCited in: 12. Special Populations & Pregnancy - [402]
Lian D, Wang D, Lin C et al.. “Early targeted next-generation sequencing accelerates clinical recovery in children with community-acquired pneumonia: A retrospective study.” Pakistan journal of medical sciences (2026). PMID: 42369922 ↗
L3COHORTCited in: 12. Special Populations & Pregnancy - [403]
Wang J, Cao J, Zhang L. “Comparative study of piperacillin-tazobactam versus ampicillin in the treatment of severe pneumonia in children: A retrospective study.” Medicine (2026). PMID: 42260869 ↗
L3COHORTCited in: 12. Special Populations & Pregnancy - [404]
Sun L, Lin H, Lin H et al.. “Characteristics and prognostic factors of patients with community-acquired pneumonia combined with pulmonary embolism: A prospective cohort study.” Medicine (2026). PMID: 42071802 ↗
L2COHORTCited in: 12. Special Populations & Pregnancy - [405]
Khreis D, Khdoud MB, El Tawil E et al.. “Outbreak of Mycoplasma pneumoniae infection in Lebanon during 2023-2024.” Journal of infection and public health (2026). PMID: 42407227 ↗
L4OTHERCited in: 12. Special Populations & Pregnancy - [406]
Eurich DT, Marrie TJ, Johnstone J et al.. “Mortality reduction with influenza vaccine in patients with pneumonia outside "flu" season: pleiotropic benefits or residual confounding?” American journal of respiratory and critical care medicine (2008). PMID: 18556629 ↗
L2OTHERCited in: 13. Prevention, Screening & Surveillance - [407]
Almirall J, Bolíbar I, Serra-Prat M et al.. “New evidence of risk factors for community-acquired pneumonia: a population-based study.” The European respiratory journal (2008). PMID: 18216057 ↗
L3OTHERCited in: 13. Prevention, Screening & Surveillance - [408]
Martínez R, Menéndez R, Reyes S et al.. “Factors associated with inflammatory cytokine patterns in community-acquired pneumonia.” The European respiratory journal (2010). PMID: 20595152 ↗
L2OTHERCited in: 13. Prevention, Screening & Surveillance - [409]
Mangen MJ, Rozenbaum MH, Huijts SM et al.. “Cost-effectiveness of adult pneumococcal conjugate vaccination in the Netherlands.” The European respiratory journal (2015). PMID: 26160871 ↗
L2OTHERCited in: 13. Prevention, Screening & Surveillance - [410]
Domínguez A, Izquierdo C, Salleras L et al.. “Effectiveness of the pneumococcal polysaccharide vaccine in preventing pneumonia in the elderly.” The European respiratory journal (2010). PMID: 20075048 ↗
L3OTHERCited in: 13. Prevention, Screening & Surveillance - [411]
Rodrigo C, Bewick T, Sheppard C et al.. “Impact of infant 13-valent pneumococcal conjugate vaccine on serotypes in adult pneumonia.” The European respiratory journal (2015). PMID: 25792633 ↗
L2OTHERCited in: 13. Prevention, Screening & Surveillance - [412]
Elemraid MA, Sails AD, Eltringham GJ et al.. “Aetiology of paediatric pneumonia after the introduction of pneumococcal conjugate vaccine.” The European respiratory journal (2013). PMID: 23598951 ↗
L2OTHERCited in: 13. Prevention, Screening & Surveillance - [413]
Kim DJ, Lee JG, Lee CY et al.. “Long-term survival following pneumonectomy for non-small cell lung cancer: clinical implications for follow-up care.” Chest (2007). PMID: 17505031 ↗
L3OTHERCited in: 13. Prevention, Screening & Surveillance - [414]
Pick H, Daniel P, Rodrigo C et al.. “Pneumococcal serotype trends, surveillance and risk factors in UK adult pneumonia, 2013-18.” Thorax (2019). PMID: 31594801 ↗
L2OTHERCited in: 13. Prevention, Screening & Surveillance - [415]
Lertussavavivat T, Isaranuwatchai S, Eiam-Ong S et al.. “Vaccine efficacy in CKD patients not on dialysis: a systematic review and meta-analysis.” Clinical kidney journal (2026). PMID: 42079457 ↗
L2SR_OBSCited in: 13. Prevention, Screening & Surveillance - [416]
Cintrón M, Gali V, Li Y et al.. “Pneumococcal serotype distribution and outcomes in cancer patients with community-acquired pneumonia: A prospective study using the 15-valent pneumococcal conjugate vaccine serotype specific urinary antigen detection assay.” International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases (2025). PMID: 41468971 ↗
L2COHORTCited in: 13. Prevention, Screening & Surveillance - [417]
Te Linde E, Wit FWNM, van Welzen BJ et al.. “Incidence of Community-acquired Pneumonia and Herpes Zoster in People With HIV Based on CD4 Count and Age in the Current Antiretroviral Therapy Era: A Longitudinal Cohort Study.” Clinical infectious diseases : an official publication of the Infectious Diseases Society of America (2026). PMID: 41406983 ↗
L2COHORTCited in: 13. Prevention, Screening & Surveillance - [418]
Sarsenov R, Solomadin M, Lavrinenko A et al.. “Microbial Etiology and Antimicrobial Resistance in Pneumonia Among Hospitalized Patients in Kazakhstan: A Systematic Review and Single-Arm Meta-Analysis of Prevalence Data.” Health science reports (2026). PMID: 42005672 ↗
L4SR_OBSCited in: 13. Prevention, Screening & Surveillance - [419]
Ankert J, Hagel S, Schwarz C et al.. “Streptococcus pneumoniae re-emerges as a cause of community-acquired pneumonia, including frequent co-infection with SARS-CoV-2, in Germany, 2021.” ERJ open research (2023). PMID: 37260459 ↗
L4OTHERCited in: 13. Prevention, Screening & Surveillance - [420]
Wang B, Zhang T, Yi L et al.. “Incidence of community-acquired pneumonia among adults between 2016 and 2023: an observational cohort study.” Epidemiology and infection (2026). PMID: 41491926 ↗
L2COHORTCited in: 13. Prevention, Screening & Surveillance - [421]
Põder A, Ong-Lim AL, Rivera Medina DM et al.. “Efficacy, immunogenicity, and safety of a cell culture-derived quadrivalent influenza vaccine compared with a non-influenza vaccine in infants and children across five influenza seasons: a phase 3, multinational, observer-blind, randomised controlled trial.” The Lancet. Child & adolescent health (2026). PMID: 41962984 ↗
L1RCTCited in: 13. Prevention, Screening & Surveillance - [422]
Tang J, Yang B, Bai Y. “Diagnostic challenges and management strategies of pulmonary mucosa-associated lymphoid tissue lymphoma: a case report and literature review.” Frontiers in medicine (2025). PMID: 41488067 ↗
L4CASE_REPORTCited in: 13. Prevention, Screening & Surveillance - [423]
Zhang J, Zhang Y, Duan C et al.. “Pediatric necrotizing pneumonia case report: clinical features, treatment experience, and prospects.” Frontiers in medicine (2025). PMID: 41041448 ↗
L4CASE_REPORTCited in: 13. Prevention, Screening & Surveillance - [424]
Xie X, Deng J, Sun G et al.. “Efficacy and safety of Omadacycline in community-acquired pneumonia among elderly patients: a real-world evidence study.” Frontiers in cellular and infection microbiology (2026). PMID: 42601885 ↗
L2bCited in: 1. Definition, Classification and Nomenclature - [425]
Loan DTK, Quang NC, Tram TV et al.. “Admission inflammatory biomarker phenotypes and risk of severe community-acquired pneumonia and PARDS in young children.” European journal of pediatrics (2026). PMID: 42570118 ↗
L2bCited in: 1. Definition, Classification and Nomenclature - [426]
Janssen NAF, Vanderbeke L, Jacobs C et al.. “Influenza-associated invasive aspergillosis in the ICU: a prospective, multicentre cohort study.” Critical care (London, England) (2025). PMID: 41318517 ↗
L2bCited in: 1. Definition, Classification and Nomenclature - [427]
Cao H, Tan S, Zhang R et al.. “Toward standardized outcome reporting in pneumonia: an overview of systematic reviews of antimicrobial therapy.” International journal of clinical pharmacy (2025). PMID: 41284209 ↗
L2aCited in: 1. Definition, Classification and Nomenclature - [428]
Zilberberg MD, Greenberg M, Nathanson BH et al.. “Epidemiology and Outcomes Among Adults With Severe Community-Acquired Bacterial Pneumonia Hospitalized in the United States, 2021-2024.” Critical care medicine (2026). PMID: 42233741 ↗
L3bCited in: 1. Definition, Classification and Nomenclature - [429]
Dieminger R, Helfrich F, Eyer F et al.. “Aspiration-induced lung injury in acute drug and ethanol poisoning: incidence, risk factors, and clinical predictors.” Clinical toxicology (Philadelphia, Pa.) (2026). PMID: 41879716 ↗
L3bCited in: 1. Definition, Classification and Nomenclature - [430]
Ramirez J, Furmanek S, Chandler T et al.. “Risk of Noncommunicable Diseases After Hospitalization for Community-Acquired Pneumonia.” Open forum infectious diseases (2026). PMID: 41852551 ↗
L3bCited in: 1. Definition, Classification and Nomenclature - [431]
Boppana LKT, Isern S, Romero KN et al.. “Necrotizing Pneumonia as a Complication of Community-Acquired Pneumonia in Adults at a Tertiary Institution.” Journal of clinical medicine (2025). PMID: 40565832 ↗
L3bCited in: 1. Definition, Classification and Nomenclature - [432]
Xiao M, Jiang Y, Chen Q et al.. “Identification of clinical phenotypes and prediction model for the mixed-infection phenotype of pediatric community-acquired pneumonia based on unsupervised machine learning.” Frontiers in pediatrics (2026). PMID: 42255918 ↗
L2bCited in: 1. Definition, Classification and Nomenclature - [433]
Dragomiretskaya NA, Tolmacheva AV, Tarzimanova AI et al.. “PIFA-N Multifactor Model to Predict Adverse Outcomes for Chronic Heart Failure Patients.” Journal of clinical medicine research (2026). PMID: 42016340 ↗
L2bCited in: 1. Definition, Classification and Nomenclature - [434]
Sun L, Zhang J, Hu S et al.. “Predictors of secondary cardiovascular events in older adults with community-acquired pneumonia: a prospective observational study.” Clinics (Sao Paulo, Brazil) (2026). PMID: 41985406 ↗
L2bCited in: 1. Definition, Classification and Nomenclature - [435]
Fraser DD, Van Nynatten LR, Tweddell D et al.. “Divergent biological pathways distinguish community-acquired pneumonia from COVID-19 despite similar plasma cytokine profiles.” Respiratory research (2025). PMID: 40887575 ↗
L4Cited in: 1. Definition, Classification and Nomenclature - [436]
Osama M, Iftikhar A, Abdul Baseer M et al.. “Assessing pneumonia severity using neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios: a cross-sectional comparison with CURB-65 score.” Therapeutic advances in infectious disease (2026). PMID: 42052251 ↗
L3bCited in: 1. Definition, Classification and Nomenclature - [437]
Voza A, Aliberti S, Bonelli F et al.. “A machine learning model including pentraxin-3 as predictor of outcomes in community-acquired pneumonia.” Journal of translational medicine (2025). PMID: 41174667 ↗
L2bCited in: 2. Pathophysiology and Mechanism - [438]
Liao J, Shen X, Du Z et al.. “Direct and indirect associations of stress hyperglycemia with delirium in older adults with community-acquired pneumonia: limited mediation by neutrophil-lymphocyte ratio and procalcitonin.” BMC geriatrics (2025). PMID: 41023857 ↗
L2bCited in: 2. Pathophysiology and Mechanism - [439]
Sell RE, Juang D, Stark P et al.. “Streptococcus anginosus Group of Bacteria as an Underappreciated Cause of Pneumonia.” Open forum infectious diseases (2025). PMID: 41054706 ↗
L4Cited in: 2. Pathophysiology and Mechanism - [440]
Guo Y, Wan N, Feng D et al.. “The value of dysregulated miR-4492/TRAF6 in diagnosis and prognosis for patients with community-acquired pneumonia.” Journal of immunology (Baltimore, Md. : 1950) (2026). PMID: 41885008 ↗
L3bCited in: 2. Pathophysiology and Mechanism - [441]
Yang XQ, Tang Q, Xiong YJ et al.. “Gut microbiota alterations and systemic inflammation in community-acquired pneumonia: a prospective gut-lung axis study.” Frontiers in immunology (2025). PMID: 41376643 ↗
L3bCited in: 2. Pathophysiology and Mechanism - [442]
Ballester F, Gabaldó-Barrios X, Jiménez-Franco A et al.. “Insights into the diagnostic and prognostic value of paraoxonase 1-related variables and inflammatory markers in community-acquired pneumonia.” Chemico-biological interactions (2025). PMID: 40516592 ↗
L3bCited in: 2. Pathophysiology and Mechanism - [443]
Zhang F, Luan J, Suo L et al.. “Altered gut microbiota and metabolite profiles in community-acquired pneumonia: a metagenomic and metabolomic study.” Microbiology spectrum (2025). PMID: 40062854 ↗
L3bCited in: 2. Pathophysiology and Mechanism - [444]
Liu Y, Guo S, Hu X et al.. “Community-acquired pneumonia with Staphylococcus aureus and viral co-infection: clinical characteristics and pathogen genomic analysis.” Journal of thoracic disease (2026). PMID: 42182636 ↗
L3bCited in: 2. Pathophysiology and Mechanism - [445]
Zhu Z. “Cumulative intravenous fluid volume in the first 24 hours and risk of respiratory deterioration in children hospitalized with community acquired pneumonia.” Frontiers in pediatrics (2026). PMID: 42038246 ↗
L3bCited in: 2. Pathophysiology and Mechanism - [446]
Daoud T, Villar J, Annane D. “Corticosteroids in ARDS: old controversies, new insights, and future directions.” Intensive care medicine (2026). PMID: 42593538 ↗
L5Cited in: 2. Pathophysiology and Mechanism - [447]
Liu Y, Ye Q. “From decline to resurgence: current perspectives on Mycoplasma pneumoniae.” Clinical microbiology reviews (2026). PMID: 42560049 ↗
L5Cited in: 2. Pathophysiology and Mechanism - [448]
Li Y, Zhao S, Su W. “Efficacy and safety of short-course antibiotic therapy for community-acquired pneumonia in adults: a meta-analysis.” Frontiers in medicine (2026). PMID: 42529044 ↗
L1aCited in: 3. Epidemiology, Etiology and Risk Factors - [449]
Kirsten H, Weis S, Ahnert P et al.. “Community-Acquired Pneumonia: Disease Course Prediction With a 5-Gene Signature.” CHEST pulmonary (2026). PMID: 42548383 ↗
L1bCited in: 3. Epidemiology, Etiology and Risk Factors - [450]
Pipitò L, Giacchino I, Mazzola CV et al.. “Community-acquired pneumonia outside the intensive care unit: Clinical characteristics and impact of rapid molecular diagnostics in the Italian SIS-NET study.” International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases (2026). PMID: 42468735 ↗
L2bCited in: 3. Epidemiology, Etiology and Risk Factors - [451]
Jiang C, Chen X, Xu X et al.. “Trends and outcomes of Mycoplasma pneumoniae pneumonia in hospitalized children before, during, and after the coronavirus disease 2019 pandemic: a retrospective study in Northeast China, 2018-2023.” Microbiology spectrum (2026). PMID: 42599103 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [452]
Yan L, Zhang H, Fu H et al.. “Targeted next-generation sequencing for pediatric community-acquired pneumonia pathogen detection: a single-center study.” Frontiers in cellular and infection microbiology (2026). PMID: 42591296 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [453]
Lam SM, Shum HP. “Doxycycline versus azithromycin as combination therapy in the empirical treatment of community-acquired pneumonia in an intensive care unit - A retrospective propensity score-matched cohort study.” Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi (2026). PMID: 42571946 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [454]
Xu H, Zhang J, Jiang S et al.. “Host inflammatory markers and MLVA profiling for risk assessment of severe pediatric Mycoplasma pneumoniae pneumonia.” Frontiers in cellular and infection microbiology (2026). PMID: 42568601 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [455]
Yang J, Song X, Wang Y et al.. “Differences and trends in pathogens between ventilator-associated pneumonia and non-ventilator-associated pneumonia: data from 61 hospitals in Suzhou, China, 2020-2024.” BMJ open (2026). PMID: 42551999 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [456]
Kong FS, Zhang LY, Wang R et al.. “The effect of type 2 diabetes on the prognosis of community-acquired pneumonia.” Frontiers in endocrinology (2026). PMID: 42523555 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [457]
Hernández Puentes JS, Bastidas AR, Tuta Quintero EA et al.. “Hydrocortisone vs. Methylprednisolone in Community-Acquired Pneumonia: A Propensity Score Matching Study.” Journal of clinical medicine (2026). PMID: 42513639 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [458]
Karcioglu AM, Atli HZ, Degdas U. “Predictive Value of SMART-COP for Adverse Outcomes in Older ICU Patients with Community-Acquired Pneumonia: A Comparison with CURB-65, SOFA, and APACHE II.” Journal of clinical medicine (2026). PMID: 42513578 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [459]
Hu F, Ji K, Gu M et al.. “Changes in the pathogenic characteristics of hospitalized children with community-acquired pneumonia in Changzhou, China, 2018-2023.” BMC infectious diseases (2026). PMID: 42471570 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [460]
Copley P, Firima E, James N et al.. “Impact of COVID-19 on sputum isolates and hospital outcomes among patients with pneumonia in Sheffield, United Kingdom: a retrospective cohort study.” Frontiers in public health (2026). PMID: 42454302 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [461]
Pulsipher AM, Khattar G, VanDolah H et al.. “Time to Effective Therapy and Mortality in Community-Acquired Legionella Pneumonia: A Multicenter Retrospective Cohort Study.” Annals of the American Thoracic Society (2026). PMID: 42435403 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [462]
Mou S, Cai Q, Xu W et al.. “Hypercapnia is associated with an increased risk of ICU admission and reduced inflammatory responses in AECOPD patients with severe pneumonia.” Therapeutic advances in respiratory disease (2026). PMID: 42429304 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [463]
Zhou D, Tang K, Zhao Y et al.. “Epidemiology, bacterial coinfection risk factors, and inflammatory markers in children with RSV, AdV, and hMPV pneumonia in Zunyi, China.” BMC infectious diseases (2026). PMID: 42387423 ↗
L3bCited in: 3. Epidemiology, Etiology and Risk Factors - [464]
Pelagatti L, De Marco M, Bosco E et al.. “RESPIRE Score: Derivation and Validation of a New Risk Score for Prediction of Community-acquired Pneumonia Caused by Resistant Pathogens.” Open forum infectious diseases (2026). PMID: 42238377 ↗
L2bCited in: 4. Clinical Presentation - [465]
Yan Z, Qian X, Liu Y et al.. “Pediatric pyopneumothorax caused by Prevotella oris successfully diagnosed via mNGS: a case report and literature review.” Frontiers in medicine (2026). PMID: 42564864 ↗
L3bCited in: 4. Clinical Presentation - [466]
Simon S, Fuge J, Hinze CA et al.. “Diagnostic discordance and differential diagnoses of community-acquired pneumonia in the emergency department.” BMC emergency medicine (2026). PMID: 42286498 ↗
L3bCited in: 4. Clinical Presentation - [467]
Wang F, Wang YW, Wang JY et al.. “Impact of pathogen co-detection on disease severity and clinical outcomes in children with Mycoplasma pneumoniae pneumonia.” World journal of pediatrics : WJP (2026). PMID: 42277482 ↗
L3bCited in: 4. Clinical Presentation - [468]
Zheng X, Wang B, Yuan L et al.. “Development and validation of machine learning-based prediction for in-hospital mortality in ICU patients with severe community-acquired pneumonia and respiratory failure.” Frontiers in medicine (2026). PMID: 42089061 ↗
L3bCited in: 4. Clinical Presentation - [469]
Chen X, Ying L, Kong W et al.. “Machine learning based development of an early diagnosis signature for distinguishing hospitalized pediatric human respiratory syncytial virus infection from mycoplasma pneumonia.” Frontiers in pediatrics (2026). PMID: 42311907 ↗
L2bCited in: 4. Clinical Presentation - [470]
Ho S, Thong PM, Yeo WS et al.. “Urinary suPAR and NGAL as biomarkers of disease severity in hospitalized adults with community-acquired pneumonia.” International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases (2026). PMID: 42468734 ↗
L2bCited in: 6. Severity, Staging and Risk Stratification - [471]
Wang M, Wang J, Liu P et al.. “Development and internal validation of a nomogram for predicting the severity of community-acquired pneumonia in children.” Frontiers in cellular and infection microbiology (2026). PMID: 42404774 ↗
L3bCited in: 6. Severity, Staging and Risk Stratification - [472]
Bielicki JA, Clements M, Musiime V et al.. “Oral step-down, optimal drug, and total duration of antibiotic treatment in African children hospitalised with severe community-acquired pneumonia (PediCAP): a factorial randomised controlled trial.” Lancet (London, England) (2026). PMID: 42492562 ↗
L1bCited in: 7. Acute Management and Exacerbation Rescue - [473]
Hagman K, Hedenstierna M, Andersson Norlén E et al.. “Adjunctive betamethasone treatment of hypoxaemic adults hospitalised with Mycoplasma pneumoniae community-acquired pneumonia: an open-label, multicentre, randomised, controlled trial.” The Lancet regional health. Europe (2026). PMID: 42099880 ↗
L1bCited in: 7. Acute Management and Exacerbation Rescue - [474]
Keisham B, Duhan S, Bajaj D et al.. “Steroid Therapy in Community-Acquired Pneumonia: An Updated Systematic Review and Meta-Analysis.” Heart & lung : the journal of critical care (2026). PMID: 42143791 ↗
L1aCited in: 7. Acute Management and Exacerbation Rescue - [475]
Yu Y, Zhang T, Xia Y et al.. “Efficacy and short-term safety of intravenous omadacycline as second-line therapy for macrolide- unresponsive Mycoplasma pneumoniae pneumonia in children: a retrospective cohort study.” Frontiers in cellular and infection microbiology (2026). PMID: 42559097 ↗
L4Cited in: 7. Acute Management and Exacerbation Rescue - [476]
Cotter JM, Dunn A, Williams DJ et al.. “Children Hospitalized With Pneumonia Who Complete Oral Antibiotic Treatment Without Complications.” Hospital pediatrics (2026). PMID: 42019953 ↗
L2bCited in: 7. Acute Management and Exacerbation Rescue - [477]
You Q, Chen Y, Yu H et al.. “Exploring a tolerable and effective dosage of omega-3 fatty acids as a supplement in enterally fed patients with severe pneumonia: A pilot study.” Asia Pacific journal of clinical nutrition (2026). PMID: 42242854 ↗
L4Cited in: 7. Acute Management and Exacerbation Rescue - [478]
Schroeder Chaidron L, Creutz E, Cremer K et al.. “Neutrophil-to-lymphocyte ratio combined with CURB-65 score to identify patients at high risk of 30-day mortality in community-acquired pneumonia through the emergency medical department of tertiary hospitals.” International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases (2026). PMID: 42341906 ↗
L4Cited in: 7. Acute Management and Exacerbation Rescue - [479]
Lv C, Liu S, Yan Y et al.. “Improved prediction value of the CURB-65 score combined with the platelet-to-lymphocyte ratio for mortality in emergency department patients with severe community-acquired pneumonia.” Frontiers in medicine (2026). PMID: 42311896 ↗
L3bCited in: 7. Acute Management and Exacerbation Rescue - [480]
Singh A, Biswal N, DelhiKumar CG et al.. “Outcome of early short course corticosteroid therapy in severe community-acquired pneumonia: a randomised controlled trial.” Archives of disease in childhood (2026). PMID: 41663239 ↗
L1bCited in: 8. Long-term and Definitive Management - [481]
Reccardini N, Confalonieri M, Ruaro B et al.. “Early C-reactive protein reduction predicts survival in COVID-19 severe pneumonia treated with glucocorticoids.” BMC pulmonary medicine (2025). PMID: 41029298 ↗
L1bCited in: 8. Long-term and Definitive Management - [482]
Theilacker C, Guardado Escobar ME, Sato R et al.. “The risk of cardiovascular, cerebrovascular and thromboembolic events after community-acquired pneumonia among adults: a systematic literature review.” European respiratory review : an official journal of the European Respiratory Society (2025). PMID: 41511415 ↗
L2aCited in: 8. Long-term and Definitive Management - [483]
Jin J, Wang Y, Weng B et al.. “The prevalence and influence of self-reported loneliness in the older with community-acquired pneumonia: a multi-center cohort study.” BMC geriatrics (2025). PMID: 41430651 ↗
L2bCited in: 8. Long-term and Definitive Management - [484]
Hegelund MH, Alam S, Dungu AM et al.. “Vitamin D Deficiency at Hospital Admission With Community-Acquired Pneumonia is Associated With Increased Risk of Mortality: A Prospective Cohort Study.” Open forum infectious diseases (2025). PMID: 41322246 ↗
L2bCited in: 8. Long-term and Definitive Management - [485]
Yao Y, Lai Y, Wu Q et al.. “Targeted next-generation sequencing improves diagnosis and antimicrobial stewardship in Chlamydia psittaci pneumonia.” European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology (2026). PMID: 41678126 ↗
L4Cited in: History and Evolution of Treatment - [486]
Oksay SC, Yörük B, Karabulut Ş et al.. “Long-Term Outcomes of Necrotizing Pneumonia and Parapneumonic Effusion in Children.” Pediatric pulmonology (2025). PMID: 40827719 ↗
L3bCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [487]
Qin H, Li X, Huang Q et al.. “Risk factors for plastic bronchitis in children with community-acquired pneumonia: a retrospective bronchoscopy-based study.” BMC pulmonary medicine (2026). PMID: 42026582 ↗
L4Cited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [488]
Chen Q, Zheng Y, Wang H et al.. “Clinical characteristics of severe community-acquired pneumonia in children with virus mono-detection versus co-detection with bacteria.” BMC pulmonary medicine (2025). PMID: 40119295 ↗
L3bCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [489]
Ryoo J, Kim SC, Lee J. “Changes in respiratory infection trends during the COVID-19 pandemic in patients with haematologic malignancy.” BMC pulmonary medicine (2024). PMID: 38797852 ↗
L3bCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [490]
Grochowska M, Strzelak A, Krenke K. “Complicated pneumonia caused by group A Streptococcus in children - 2022/2023 infectious season outbreak and update on clinical characteristics.” Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy (2024). PMID: 38631479 ↗
L3bCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [491]
Wang X, Lu Y, Chen F et al.. “Clinical characteristics of pediatric patients hospitalized with community-acquired pneumonia and cytomegalovirus DNA detected in bronchoalveolar lavage fluid.” Frontiers in pediatrics (2024). PMID: 39114856 ↗
L3bCited in: 9. Respiratory Support, Procedures & Interventional Pulmonology (Specialty-Distinctive) - [492]
Meng L, Cheng A, Tang D et al.. “Molecular Epidemiology, Viral Load and Clinical Severity of Human Adenovirus-Associated Respiratory Infections in Hospitalized Children in Shanghai, 2021-2023.” Journal of medical virology (2026). PMID: 42312585 ↗
L3bCited in: 10. Complications - [493]
Arnés-García D, Calderón-Parra J, Calvo-Salvador M et al.. “Clinical Experience of Ceftaroline Fosamil in Gram-Positive Infective Endocarditis: A Multicenter Real-World Observational Study.” Antibiotics (Basel, Switzerland) (2026). PMID: 42192688 ↗
L4Cited in: 10. Complications - [494]
Miura S, Michihata N, Isogai T et al.. “Corticosteroid use and mortality of severe community-acquired pneumonia in children: A propensity score-matched analysis.” Journal of intensive care medicine (2025). PMID: 42048066 ↗
L3bCited in: 10. Complications - [495]
Zhang K, Ji W, Yang H et al.. “Clinical characteristics and risk factors associated with mortality in patients with severe community-acquired pneumonia in the intensive care unit.” Journal of thoracic disease (2026). PMID: 42306673 ↗
L2bCited in: 10. Complications - [496]
Çapar ISK, Tural-Kara T. “Risk Stratification for Complications in Patients Hospitalized With Community-Acquired Pneumonia.” Journal of paediatrics and child health (2026). PMID: 42083133 ↗
L2bCited in: 10. Complications - [497]
Jing X, Jiang K, Tang H. “A single tertiary hospital-based retrospective observational study on epidemiological features and clinical correlates of severe pediatric Chlamydia pneumoniae pneumonia in post-pandemic in Shanghai.” Translational pediatrics (2026). PMID: 42591710 ↗
L4Cited in: 10. Complications - [498]
An J, Du S, Yu S et al.. “Clinical Characteristics and Early Risk Factors for Severe Mycoplasma Pneumoniae Pneumonia in Hospitalized Children: A Retrospective Analysis of 417 Cases.” Infection and drug resistance (2026). PMID: 41978617 ↗
L3bCited in: 10. Complications - [499]
Stavăr-Matei L, Țocu L, Nechita A et al.. “Pneumococcal Detection and Bacterial Co-Detection in Children After COVID-19: A Two-Year Multiplex PCR Study.” Biomedicines (2026). PMID: 42351809 ↗
L3bCited in: 12. Special Populations & Pregnancy - [500]
Lim J, Cha K, Kim HJ. “Walking ability as a prognostic indicator in elderly patients with community-acquired pneumonia: a retrospective multicenter study.” BMC geriatrics (2026). PMID: 42210166 ↗
L3bCited in: 12. Special Populations & Pregnancy - [501]
Pulsipher AM, Khattar G, Harris E et al.. “Legionella 5S rRNA PCR melting temperature analysis discriminates high-risk species associated with disease severity.” Journal of clinical microbiology (2026). PMID: 42214385 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [502]
Kononoff J, Anttila VJ, Klemets P et al.. “Burden of Invasive Pneumococcal Disease and Community-Acquired Pneumonia in Adults: Significant Adverse Outcomes and Costs beyond Direct Treatment.” Infectious diseases and therapy (2026). PMID: 42143198 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [503]
Lan Y, Xin Z, Lin Z et al.. “Heterogeneity in the Association Between Pneumococcal Vaccination and the Risk of Severe Community-Acquired Pneumonia in Elderly Inpatients: A Causal Forest Analysis.” Vaccines (2026). PMID: 41601006 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [504]
Froes F, Diniz A, Mergulhão P et al.. “Evolution of hospitalizations of adults for Community-Acquired Pneumonia in Portugal and the impact of pediatric pneumococcal vaccination.” Pulmonology (2025). PMID: 41324479 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [505]
Yang T, Ying X, Wu X et al.. “Protection and Duration of 23-Valent Pneumococcal Polysaccharide Vaccine Against Hospitalization for Community-Acquired Pneumonia in Older Adults with Low Vaccination Coverage: A Multicenter Matched Case-Control Study in China.” Vaccines (2026). PMID: 42506683 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [506]
Tekle MT, Jara AG, Sema FD. “Thirty-day hospital readmission and its determinants among patients with severe community-acquired pneumonia: a prospective cross-sectional study in Northwest Ethiopia.” BMC infectious diseases (2026). PMID: 41845245 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [507]
Yan C, Tong S, Wu Y et al.. “Macrolide-resistant Mycoplasma pneumoniae resurgence in Chinese children in 2023: a longitudinal, cross-sectional, genomic epidemiology study.” The Lancet. Microbe (2025). PMID: 41325763 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [508]
Di Giovanni P, Di Martino G, Petrangelo M et al.. “The Burden of Streptococcus Pneumoniae-Related Admissions in Pediatric Population: A Retrospective Cohort Study Between Years 2018-2023 From a Southern Italian Region.” Health science reports (2026). PMID: 42466376 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [509]
Xia Z, Zhang H, Xu S et al.. “Changes in pediatric pneumonia incidence and pathogen spectrum before, during, and after the COVID-19 pandemic: an eight-year inpatient data analysis from a tertiary hospital in Fujian, China.” BMC pediatrics (2026). PMID: 42168946 ↗
L3bCited in: 13. Prevention, Screening & Surveillance - [510]
Ali S, Burns K, Dinesh B et al.. “Is the pneumococcal urinary antigen test still fit for purpose? a decade of experience.” Diagnostic microbiology and infectious disease (2026). PMID: 41895087 ↗
L3bCited in: 13. Prevention, Screening & Surveillance