The incidence of bloodstream infections caused by anaerobic bacteria in a university hospital between 2005-2009 and 2013-2017 A retrospective, comparative study

Introduction: Anaerobes play an important etiological role in invasive infections, and may be clinically significant pathogens in bloodstream infections and septicemia, but little data are available on their true prevalence in Hungary. Aim: The aim of this study was to determine the prevalence of anaerobic bacteria in the blood culture samples received at the Institute of Clinical Microbiology, University of Szeged, retrospectively. Method: Blood culture samples received at the Institute were analyzed over a 5-year period (01. 01. 2013-31. 12. 2017); the comparison was based on a similar study (2005-2009) conducted in the same region. Results: Between 2013 and 2017, our Institute received an average of 23,274 +/- 2,756 blood culture bottles, of which an average of 10.5% were positive and 0.4% were positive for anaerobes (3.5-3.8/1000 bottles). Clinically significant anaerobic pathogens were predominantly Bacteroides fragilis group (39.9%) and Clostridium species (32.8%). Conclusion: Despite their relatively low numbers, anaerobic bacteria are considered important etiologic factors in bloodstream infections. Our results highlight the importance of modern identification methods in adequate anaerobic diagnostics.