OBJECTIVE: Routine clinical practice with extended anaerobic antibiotic coverage (EAC) has been recently reconsidered for several infections
however, its benefits remain unclear even in patients with anaerobic bacteremia (AB). Here, we aimed to elucidate the effects of EAC on AB prognosis. METHODS: A multicenter retrospective observational study was conducted in patients with AB. Multivariate logistic regression analysis was performed to assess the effect of EAC on 30-day mortality. Inverse probability of treatment weighting analysis was performed to confirm the robustness of the findings. RESULTS: In total, 483 patients were included, of whom 387 received EAC and 96 received limited anaerobic antibiotic coverage (LAC). Atypical foci of anaerobic infection, such as urinary tract infection and pneumonia, together with undetectable infection foci, comprised a larger proportion of infection foci in the LAC group than that in the EAC group (46.9% vs. 30.5%). The 30-day mortality rates of the EAC and LAC groups were similar (12.5% and 14.2%, respectively
p=0.664). Primary analysis revealed that EAC was not significantly associated with high mortality (odds ratio [OR], 1.42
95% confidence interval [CI], 0.7-2.8), whereas source control significantly reduced this risk (OR, 0.28
95% CI, 0.2-0.5). The sensitivity analysis results were consistent with those of the primary analyses. CONCLUSIONS: This study demonstrated a less significant effect of initial EAC on AB compared with source control, particularly on AB with atypical infection foci. These findings would prompt reconsideration of the necessity of an initial EAC in several infections.