The utility of anaerobic blood culture

Abstract

Anaerobic bacteria have been implicated in many significant human infections, with a reported mortality of up to 38% in bacteraemia. Current data suggest anaerobic pathogens account for 0.4–7% of all positive blood cultures. Notwithstanding this data there is no consensus with regards to the utility of anaerobic blood culture. The counter argument is a low incidence and predictable risk factors and therefore potential limited therapeutic gain. The aim of our study was to determine the incidence of anaerobic bacteraemia and the causative organisms at our facility. From 2000 to 2017, 18,411 positive blood cultures were reviewed. A total of 408 (2.2%) anaerobic isolates were identified, with 322 (1.7%) deemed clinically significant. The most commonly isolated anaerobic genera were Bacteroides, Propionibacterium, Clostridium, Peptostreptococcus and Fusobacterium. The anaerobic bottle was singularly positive in 279 (95%) of cases. Therefore, although anaerobic bacteraemia is infrequent at our facility, omission of anaerobic blood culture bottles is likely to result in missed diagnoses and potentially inadequate therapy. Given the high mortality of anaerobic bacteraemia, routine use of both aerobic and anaerobic blood culture bottles is justified.