The in vitro susceptibilities of Bacteroides fragilis to antimicrobial agents, especially to carbapenem, are a major concern in the treatment of patients with bloodstream infections. In this study, 50 isolates of B. fragilis were obtained from positive blood bottles from 2014 to 2019 in Saitama, Japan. Their susceptibility to ampicillin/sulbactam was reduced to 70.0% compared with a previous report, whereas they were still sufficiently susceptible to piperacillin/tazobactam (94.0%). Five cfiA-positive isolates (5/50, 10.0%) were identified that were resistant to doripenem and meropenem, and two of them carried an insertion sequence located upstream of the cfiA-coding region. In particular, imipenem should be considered as a first-line carbapenem for the empirical treatment of B. fragilis infection because only insertion sequence and cfiA double-positive strains showed resistance to imipenem. Thirty-six percent of the isolates had a reduced minimum inhibitory concentration for moxifloxacin. In addition, metronidazole should still be considered as an active agent for B. fragilis because all isolates were susceptible to this antibiotic and the prevalence of the nim gene was low in Japan.

在体外的敏感性脆弱拟杆菌抗菌药物，尤其是碳青霉烯类，在患者的血液感染治疗的主要问题。在这项研究中，从2014年至2019年在日本琦玉的阳性血瓶中获得了50株脆弱的B.fragilis分离株。与先前的报道相比，他们对氨苄西林/舒巴坦的敏感性降低到70.0％，而他们仍然对哌拉西林/他唑巴坦足够敏感（94.0％）。鉴定出五株对多立培南和美洛培南具有抗性的cfiA阳性分离株（5 / 50，10.0％），其中两株带有位于cfiA上游的插入序列编码区域。特别是，亚胺培南应被视为经验性治疗脆弱性芽孢杆菌的一线碳青霉烯，因为只有插入序列和cfiA双阳性菌株对亚胺培南具有抗性。36％的分离物对莫西沙星的最低抑菌浓度降低。此外，甲硝唑仍应被认为是脆弱芽孢杆菌的活性剂，因为所有分离株均对这种抗生素敏感，并且nim基因在日本的患病率较低。