Community-onset anaerobic bloodstream infection, predisposing factors, and impact on survival: A prospective cohort study

Abstract

BackgroundFew studies have examined the outcomes and predisposing risk factors for anaerobic bloodstream infections (BSIs). ObjectiveTo determine the survival impact of aerobic versus anaerobic BSI, a prospective cohort study was conducted. MethodsWe prospectively enrolled emergency department patients at a tertiary medical center with BSIs determined by laboratory testing between 2015 and 2016. Anaerobic and aerobic BSIs were compared for demographics, comorbidities, and sources of infection. Several independent risk factors were identified in a multivariable logistic regression model. Using propensity score (PS) matched data, an analysis of survival effects associated with anaerobic BSI has been conducted. ResultsOver a 2-year period, there were 1,166 episodes of BSI, of which 61 (5.2%) occurred as anaerobic episodes. Anaerobic BSIs were strongly associated with intra-abdominal infection (odds ratio [OR] 6.03, 95%CI 2.78–13.09), liver abscess (OR 3.92, 95%CI 1.47–10.45), skin and soft-tissue infection (OR 2.65, 95%CI 1.26–5.62), and metastatic cancer (OR 2.40, 95%CI 1.13–5.08) as the main positive predictors. Negative predictors included diabetes mellitus (OR 0.38, 95%CI 0.18–0.78), thrombocytopenia (OR 0.33, 95%CI 0.18–0.60), and urinary tract infection (OR 0.15, 95%CI 0.04–0.62). Anaerobic BSIs were not associated with worse prognosis after PS-matched analysis (hazard ratio [HR] 1.40, 95%CI 0.44–4.41) in our cohort. ConclusionsA significant percentage of community-onset BSI was due to anaerobic BSI. Anaerobic BSI can have a detrimental outcome if there are underlying comorbidities, high-risk infection sites, and inappropriate antibiotic choices. The findings of our study may contribute to the prescription of empiric anti-anaerobe antibiotics.