Background Bacteroides fragilis group (BFG) isolates are the most frequently isolated gram-negative anaerobic bacteria and exhibit higher levels of antimicrobial resistance than other anaerobic bacteria. Reliable susceptibility testing is needed because of reports of resistance to the most active antibiotics. Recently, the European Committee on Antimicrobial Susceptibility Testing (EUCAST) introduced disk zone diameter breakpoints. We evaluated the disk diffusion test (DDT) for susceptibility testing of BFG isolates compared with the agar dilution method. Methods In total, 150 BFG isolates were collected from three institutes in Korea. The agar dilution method was conducted according to the CLSI guidelines. DDT was performed following the EUCAST guideline. Fastidious anaerobe agar supplemented with 5% defibrinated horse blood was used as the culture medium. Nine antimicrobials were evaluated: penicillin, cefoxitin, cefotetan, imipenem, meropenem, piperacillin-tazobactam, clindamycin, moxifloxacin, and metronidazole. Results The categorical agreement (CA) between the two methods was >90.0% for imipenem, meropenem, clindamycin, and metronidazole. However, the CA for piperacillintazobactam was low, at 83.2%. Major errors were found: 5.4% for imipenem, 7.4% for meropenem, and 12.8% for piperacillin-tazobactam. All minor errors were <10%. We propose using the area of technical uncertainty (ATU) zone-overlapping area for susceptible and resistant strains to reduce errors in the DDT. Outside the ATU, the CAs of cefoxitin, cefotetan, and piperacillin-tazobactam were >90.0%, whereas that of moxifloxacin was increased to 88.5%. Conclusions The DDT can be a useful alternative antimicrobial susceptibility test for BFG isolates when using the ATU zone to reduce errors.

中文翻译：

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脆弱拟杆菌组临床分离株纸片扩散试验的评估。


背景脆弱拟杆菌群 (BFG) 分离株是最常分离的革兰氏阴性厌氧菌，并且比其他厌氧菌表现出更高水平的抗菌素耐药性。由于有报道称对最活跃的抗生素有耐药性，因此需要可靠的药敏试验。最近，欧洲抗菌药物敏感性测试委员会 (EUCAST) 引入了圆盘区域直径断点。我们评估了纸片扩散试验 (DDT) 与琼脂稀释法相比对 BFG 分离株的药敏试验。方法从韩国三个研究所总共收集了 150 株 BFG 分离株。琼脂稀释方法根据 CLSI 指南进行。 DDT 是按照 EUCAST 指南进行的。使用添加有5％去纤维马血的挑剔厌氧菌琼脂作为培养基。评估了九种抗菌药物：青霉素、头孢西丁、头孢替坦、亚胺培南、美罗培南、哌拉西林-他唑巴坦、克林霉素、莫西沙星和甲硝唑。结果 对于亚胺培南、美罗培南、克林霉素和甲硝唑，两种方法之间的分类一致性 (CA) 为 >90.0%。然而，哌拉西林唑巴坦的 CA 较低，为 83.2%。发现主要错误：亚胺培南为 5.4%，美罗培南为 7.4%，哌拉西林-他唑巴坦为 12.8%。所有小错误均为<10%。我们建议使用敏感菌株和耐药菌株的技术不确定性 (ATU) 区域重叠区域来减少 DDT 中的错误。在ATU之外，头孢西丁、头孢替坦和哌拉西林-他唑巴坦的CA为>90.0%，而莫西沙星的CA增加至88.5%。结论 当使用 ATU 区减少错误时，DDT 可以成为 BFG 分离株的一种有用的替代抗菌药物敏感性测试。