Clinical and Epidemiologic Characteristics of Anaerobic Bacteria Originating from Blood Cultures: A Five-Year Retrospective Study

Why clinicians should know about it

• Picked for Microbiology (medical) (paper of the day, 20 July 2026).

Abstract

BACKGROUND: With the rise of anaerobic bacteremia and resistance to anaerobes for commonly used agents, the resistance patterns of many anaerobes have changed significantly among different geographic areas and medical facilities. This study investigated the clinical and epidemiologic characteristics of anaerobic bacteremia for therapeutic optimization at the local level. METHODS: This retrospective observational study included all positive blood cultures (BC) from 2020 to 2024. For patients with anaerobic bacteria originating from BCs, clinical and microbiological data were collected. RESULTS: In total, 239 anaerobic strains were isolated from 223 patients. Among BC-positive bacteria, the proportion of anaerobes accounted for 4.4% (239/5450), with a gradual increase from 3.0% in 2020 to 6.1% in 2024. The most common anaerobes were Bacteroides fragilis (34.7%) and Cutibacterium acnes (20.5%). The resistance rates of gram-negative anaerobes to penicillin, imipenem, and meropenem were 94.4%, 21.1%, and 35.2%, respectively, which were much higher than those of gram-positive anaerobes (16.7%, 0%, 0%). Among the 223 cases, abdominal disorders were the most frequent underlying condition (54.7%). In the empirical antibiotic therapy, 94.6% of the patients received β-lactam antibiotics, and the infection symptoms improved in 74.9% of the patients. For Bacteroides spp. bacteremia, the improvement rate in patients treated with carbapenems and β-lactam/β-lactamase inhibitor combinations was 78.1% and 40.0%, respectively. CONCLUSION: The study presents valuable data for monitoring and improving anaerobic bacteremia treatment in Southern of China.

Abstract as published, via PubMed.