Anaerobic bloodstream infections in Italy (ITANAEROBY): A 5-year retrospective nationwide survey

Introduction: A lack of updated data on the burden and profile of anaerobic bloodstream infections (ABIs) exists. We assessed the incidence of ABIs and trends in antimicrobial resistance in anaerobes isolated from blood in Italy. Material and methods: We conducted a retrospective study on 17 Italian hospitals (2016-2020). Anaerobes isolated from blood culture and their in vitro susceptibility profiles (EUCAST-interpreted) were registered and analyzed. Results: A total of 1960 ABIs were identified. The mean age of ABIs patients was 68.6 +/- 18.5 years, 57.6% were males. The overall incidence rate of ABIs was 1.01 per 10.000 patient-days. Forty-seven% of ABIs occurred in medical wards, 17% in ICUs, 14% in surgical wards, 7% in hemato-oncology, 14% in outpatients. The three most common anti-anaerobic tested drugs were metronidazole (92%), clindamycin (89%) and amoxicillin/clavulanate (83%). The three most common isolated anaerobes were Bacteroides fragilis (n = 529), Cutibacterium acnes (n = 262) and Clostridium perfringens (n = 134). The lowest resistance rate (1.5%) was to carbapenems, whereas the highest rate (51%) was to penicillin. Clindamycin resistance was >20% for Bacteroides spp., Prevotella spp. and Clostridium spp. Metronidazole resistance was 9.2% after excluding C. acnes and Actinomyces spp. Bacteroides spp. showed an increased prevalence of clindamycin resistance through the study period: 19% in 2016, 33% in 2020 (p < 0.001). Conclusions: Our data provide a comprehensive overview of the epidemiology of ABIs in Italy, filling a gap that has existed since 1995. Caution is needed when clindamycin is used as empirical anti-anaerobic drug. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This study provides updated data on the burden and profile of anaerobic bloodstream infections (ABIs) in Italy. The findings show that the average age of ABIs patients is relatively high, with a majority being males. The susceptibility testing of antibiotics reveals a low resistance rate to metronidazole and a high resistance rate to penicillin among anaerobes. The resistance of Bacteroides spp. to clindamycin has increased over the study period. These results offer a comprehensive overview of the epidemiology of ABIs.