Incidence and Clinical Characteristics of Anaerobic Bacteremia at a University Hospital in Hungary: A 5-Year Retrospective Observational Study

Abstract

Strict anaerobes have been reported to account for 0.5-13% of episodes of bacteremia in the adult population, with a growing awareness among clinicians regarding anaerobic bacteremia, especially in patients with specific predisposing factors. The aim of our present study was to assess the incidence and clinical characteristics of anaerobic bacteremia during a 5-year period (2016-2020) at a tertiary care teaching hospital, and to compare our findings with other studies in Hungary. Overall, n = 160 strict anaerobes were detected, out of which, 44.4% (n = 71; 0.1% of positive blood cultures, 0.1/1000 hospitalizations, 3.3/100,000 patient days) were clinically significant, while Cutibacterium spp. accounted for 55.6% (n = 89) of isolates. Among relevant pathogens, the Bacteroides/Parabacteroides spp. group (32.4%; n = 23), Clostridium spp. (22.5%; n = 16) and Gram-positive anaerobic cocci (15.5%; n = 11) were the most common. The mean age of patients was 67.1 ± 14.1 years, with a male majority (59.2%; n = 42). A total of 38.0% of patients were affected by a malignancy or immunosuppression, while an abscess was identified in 15.5% of cases. A total of 74.7% (n = 53) of patients received antibiotics prior to blood culture sampling; in instances where antimicrobials were reported, anaerobic coverage of the drugs was appropriate in 52.1% (n = 37) of cases. The 30-day crude mortality rate was 39.4% (n = 28); age ≥ 75 years was a significant predictor of 30-day mortality (OR: 5.0; CI: 1.8-14.4; p = 0.003), while malignancy and immunosuppression, lack of anti-anaerobic coverage or female sex did not show a significant relationship with the mortality of these patients. Early recognition of the role played by anaerobes in sepsis and timely initiation of adequate, effective antimicrobial treatment have proven efficient in reducing the mortality of patients affected by anaerobic bacteremia.

Keywords: Bacteroides; Clostridium; MALDI-TOF; anaerobes; bacteremia; blood cultures; bloodstream infections; clinical study.