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Infectious Diseases›Condition·Updated Jun 27, 2026·v1

Bacterial Meningitis (Opus)

Acute community-acquired bacterial meningitis is a neurological emergency, most often caused by [[Streptococcus pneumoniae]] and [[Neisseria meningitidis]] in adults, in which delay to effective antibiotics and adjunctive [[dexamethasone]] directly worsens death and disability.

Low Evidence21 references·6,072 words·25 min read·v1
Infectious DiseasesNeurologyCNS Infection

Quick Reference

RxDrug of choiceCeftriaxone + vancomycin (+ ampicillin if Listeria risk); dexamethasone with first dose
AltAlternativesMeropenem (beta-lactam allergy / Gram-negative cover); moxifloxacin or aztreonam plus vancomycin in severe penicillin/cephalosporin allergy; trimethoprim-sulfamethoxazole for Listeria if penicillin-allergic
⊘AvoidDelaying antibiotics to obtain neuroimaging or LP; LP without prior CT when there are focal deficits, new seizures, severe immunocompromise, papilledema, or GCS-defined coma per IDSA criteria
DxTest of choiceLumbar puncture / CSF analysis
ScKey scoreGlasgow Coma Scale (admission GCS is the strongest clinical prognostic input); MRC/Dutch meningitis risk score for research staging
→When to referImmediate ICU/infectious-diseases and neurology involvement for coma, focal deficits, seizures, septic shock, or need for neurosurgical source control (CSF leak, mastoiditis, abscess).
Suspected bacterial meningitis is a door-to-antibiotic emergency: draw blood cultures, give dexamethasone with the first antibiotic, do LP promptly unless strict CT-before-LP criteria apply, and start ceftriaxone + vancomycin (+ ampicillin if Listeria risk).

Overview and Recommendations

Background

  • •Acute community-acquired bacterial meningitis (ABM) is purulent inflammation of the leptomeninges and subarachnoid space; in Dutch and Swedish nationwide cohorts S. pneumoniae causes 51-72% and N. meningitidis the next largest share [1][2].
  • •Despite vaccines and modern antibiotics, in-hospital mortality remains roughly 17-21% overall and ~30% for pneumococcal disease, with unfavorable outcome in 34-38% of episodes [1][2].
  • •The classic triad of fever, neck stiffness and altered mental status is present in only ~44% of adults, but ~95% have at least two of headache, fever, neck stiffness, or altered mentation [1].

Key Points

  • •Do not delay antibiotics for CT or LP; prompt lumbar puncture is associated with lower mortality and more favorable outcome [7].
  • •Adjunctive 0.15 mg/kg q6h, started with or before the first antibiotic dose, reduces unfavorable outcome and mortality in high-income adult pneumococcal meningitis [3][4].
  • •Empiric therapy of choice in adults is plus , adding when risk is present (age >50, pregnancy, immunocompromise) [18].

Board Review — High Yield

  • •Classic triad — fever + neck stiffness + altered mental status is present in only ~44% of adults; ~95% have at least two of headache/fever/neck stiffness/altered mentation [1].
  • •Commonest pathogen — S. pneumoniae is the leading adult cause (51-72%) and carries the highest mortality (~30%) [1][2].
  • •Dexamethasone — 10 mg (0.15 mg/kg) q6h x4 days with/before first antibiotic reduced unfavorable outcome (RR 0.59) and death (RR 0.48), mainly in pneumococcal disease [3].
  • •Listeria cover — add ampicillin for age >50, pregnancy, alcoholism, or cell-mediated immunocompromise; cephalosporins do NOT cover Listeria [18].
  • •LP timing — prompt LP (vs imaging-first) is associated with lower mortality (aOR 0.38) and better outcome; impaired mental status and immunosuppression alone are not indications to image first [7].
  • •CSF lactate — at a >7.2 mmol/L cutoff distinguished bacterial from viral meningitis with ~93% sensitivity and 100% specificity in one prospective study [19].
  • •Gold standard — CSF (and blood) culture is the reference standard for diagnosis and susceptibility [1][18].
  • •Recurrent meningitis — ~6% of episodes; think CSF leak and ENT (otitis/sinusitis) sources, predominantly pneumococcal [9].
  • •Strongest poor-outcome predictors — advanced age, low admission GCS, tachycardia, positive blood culture, low CSF white-cell count, and pneumococcal etiology [1][2].

Deep Dive — Evidence Details

References

  1. [1]

    van de Beek D, de Gans J, Spanjaard L, Weisfelt M, Reitsma JB, Vermeulen M. “Clinical features and prognostic factors in adults with bacterial meningitis.” N Engl J Med (2004). PMID: 15509818 ↗

    Prospective cohort
  2. [2]

    Bijlsma MW, Brouwer MC, Kasanmoentalib ES, Kloek AT, Lucas MJ, Tanck MW, van der Ende A, van de Beek D. “Community-acquired bacterial meningitis in adults in the Netherlands, 2006-14: a prospective cohort study.” Lancet Infect Dis (2015). PMID: 26652862 ↗

    Prospective cohort
  3. [3]

    de Gans J, van de Beek D. “Dexamethasone in adults with bacterial meningitis.” N Engl J Med (2002). PMID: 12432041 ↗

    Randomized controlled trial
  4. [4]

    van de Beek D, de Gans J, McIntyre P, Prasad K. “Corticosteroids for acute bacterial meningitis.” Cochrane Database Syst Rev (2007). PMID: 17253505 ↗

    Systematic review / meta-analysis
  5. [5]

    van de Beek D, Farrar JJ, de Gans J, Mai NT, Molyneux EM, Peltola H, et al.. “Adjunctive dexamethasone in bacterial meningitis: a meta-analysis of individual patient data.” Lancet Neurol (2010). PMID: 20138011 ↗

    Individual-patient meta-analysis
  6. [6]

    Weisfelt M, Hoogman M, van de Beek D, de Gans J, Dreschler WA, Schmand BA. “Dexamethasone and long-term outcome in adults with bacterial meningitis.” Ann Neurol (2006). PMID: 16958121 ↗

    RCT follow-up
  7. [7]

    Glimaker M, Sjolin J, Akesson S, Naucler P. “Lumbar Puncture Performed Promptly or After Neuroimaging in Acute Bacterial Meningitis in Adults: A Prospective National Cohort Study Evaluating Different Guidelines.” Clin Infect Dis (2018). PMID: 29020334 ↗

    Prospective cohort
  8. [8]

    Costerus JM, Lemmens CMC, van de Beek D, Brouwer MC. “Cranial Imaging and Lumbar Puncture in Patients With Suspected Central Nervous System Infection.” Clin Infect Dis (2020). PMID: 31437271 ↗

    Cohort study
  9. [9]

    ter Horst L, Brouwer MC, van der Ende A, van de Beek D. “Recurrent Community-Acquired Bacterial Meningitis in Adults.” Clin Infect Dis (2021). PMID: 33751028 ↗

    Prospective cohort
  10. [10]

    van Soest TM, Sondermolle MB, Brouwer MC, Chekrouni N, Larsen AR, Petersen A, et al.. “Community-acquired Staphylococcus aureus meningitis in adults.” J Infect (2023). PMID: 36682629 ↗

    Prospective cohort
  11. [11]

    Ranzenigo M, van Soest TM, Hensen EF, Cinque P, Castagna A, Brouwer MC, van de Beek D. “Otitis in Patients With Community-Acquired Bacterial Meningitis: A Nationwide Prospective Cohort Study.” Clin Infect Dis (2024). PMID: 38655694 ↗

    Prospective cohort
  12. [12]

    Chekrouni N, Koelman DLH, Brouwer MC, van der Ende A, van de Beek D. “Community-acquired Haemophilus influenzae meningitis in adults.” J Infect (2021). PMID: 33774020 ↗

    Prospective cohort
  13. [13]

    Subramanian K, Henriques-Normark B, Normark S. “Emerging concepts in the pathogenesis of the Streptococcus pneumoniae: From nasopharyngeal colonizer to intracellular pathogen.” Cell Microbiol (2019). PMID: 31251447 ↗

    Review
  14. [14]

    Brown AO, Millett ERC, Quint JK, Orihuela CJ. “Cardiotoxicity during invasive pneumococcal disease.” Am J Respir Crit Care Med (2015). PMID: 25629643 ↗

    Review
  15. [15]

    Chen JQ, Li NN, Wang BW, Liu XF, Liu JL, Chang Q. “Upregulation of CBP by PLY can cause permeability of blood-brain barrier to increase meningitis.” J Biochem Mol Toxicol (2019). PMID: 30980515 ↗

    Experimental
  16. [16]

    Bijlsma MW, Brouwer MC, Bossuyt PM, Heymans MW, van der Ende A, Tanck MWT, van de Beek D. “Risk scores for outcome in bacterial meningitis: Systematic review and external validation study.” J Infect (2016). PMID: 27519619 ↗

    Systematic review / validation
  17. [17]

    van Samkar A, Brouwer MC, Pannekoek Y, van der Ende A, van de Beek D. “Streptococcus gallolyticus meningitis in adults: report of five cases and review of the literature.” Clin Microbiol Infect (2015). PMID: 26314916 ↗

    Case series / systematic review
  18. [18]

    Mount HR, Boyle SD. “Aseptic and Bacterial Meningitis: Evaluation, Treatment, and Prevention.” Am Fam Physician (2017). PMID: 28925647 ↗

    Guideline-based review
  19. [19]

    Arafa ZAA, Gabr MS, Kamel EM, ElMasry SA, Fahim NA. “Cerebrospinal Fluid Lactate as a Differential Biomarker for Bacterial and Viral Meningitis.” Egypt J Immunol (2023). PMID: 37440535 ↗

    Diagnostic accuracy
  20. [20]

    Kremer PHC, Lees JA, Koopmans MM, Ferwerda B, Arends AWM, Feller MM, et al.. “Benzalkonium tolerance genes and outcome in Listeria monocytogenes meningitis.” Clin Microbiol Infect (2016). PMID: 27998823 ↗

    Cohort / genomic
  21. [21]

    Cohen R, Biscardi S, Levy C. “The multifaceted impact of pneumococcal conjugate vaccine implementation in children in France between 2001 to 2014.” Hum Vaccin Immunother (2016). PMID: 26905678 ↗

    Review

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