Laboratoire de Bactériologie-Hygiène, CHU de Toulouse, Université de Toulouse Paul Sabatier, Toulouse, France.
Digestive Health Research Institute (IRSD), National Institute of Health and Medical Research (INSERM), Université de Toulouse Paul Sabatier, National Research Institute for Agriculture, Food and the Environment (INRAE), National Veterinary School of Toulouse (ENVT), Toulouse, France.
J Antimicrob Chemother. 2024 Oct 1;79(10):2645-2652. doi: 10.1093/jac/dkae271.
Performance evaluation of routine laboratory methods to determine the susceptibility of Enterobacterales urinary isolates to fosfomycin (oral administration) and mecillinam.
We collected 347 Enterobacterales isolates from monomicrobial midstream urine samples from women with significant bacteriuria and leukocyturia. Mostly non-Escherichia coli isolates (i.e. Klebsiella spp., Citrobacter koseri, Enterobacter cloacae complex and Proteus mirabilis) were included (n = 298). Performance of VITEK®2, ETEST®, and disc diffusion to determine fosfomycin and mecillinam susceptibility was evaluated following International Organization for Standardization (ISO) 20776-2:2021 (or 20776-2:2007 for disc diffusion) in comparison with the agar dilution reference method.
For fosfomycin testing, VITEK®2 and ETEST® were close to reaching ISO requirements (essential agreement ≥ 90%; bias ±30%) for C. koseri, E. coli and P. mirabilis. Categorical agreement (CA) and major error rates were acceptable for disc diffusion. Fosfomycin displayed lower activity against E. cloacae complex and Klebsiella spp., with MIC50 (minimum inhibitory concentration required to inhibit the growth of 50% of tested isolates) equal to the E. coli EUCAST breakpoint (8 mg/L). For these species, the three alternative techniques overestimated MICs and resistance, and did not meet performance criteria. For mecillinam testing of Enterobacterales isolates, apart from P. mirabilis, ETEST® nearly fulfilled ISO requirements, and CA rates were acceptable for disc diffusion. ISO criteria were reached for C. koseri and E. coli testing with VITEK®2, apart from too high rates of very major errors. For P. mirabilis, performances were unacceptable, whatever the routine method used.
Commercially available tests may serve as alternatives to agar dilution to assess fosfomycin (oral) and mecillinam susceptibility of Enterobacterales urinary isolates, with important interspecies variabilities. Additional studies comprising more fosfomycin- and mecillinam-resistant isolates are needed to strengthen our conclusions.
评估常规实验室方法对肠杆菌科尿路感染分离株对磷霉素（口服）和美西林的药敏性的检测性能。
我们收集了 347 株来自女性单纯性菌尿和白细胞尿的肠杆菌科分离株。主要包括非大肠埃希菌分离株（即肺炎克雷伯菌、产酸克雷伯菌、阴沟肠杆菌复合体和奇异变形杆菌）（n=298）。根据国际标准化组织（ISO）20776-2:2021 （或 20776-2:2007 用于纸片扩散法）评估 VITEK ® 2、Etest ® 和纸片扩散法检测磷霉素和美西林敏感性的性能，与琼脂稀释参考方法进行比较。
对于磷霉素检测，VITEK ® 2 和 Etest ® 接近达到 ISO 要求（基本一致率≥90%；偏差±30%），适用于产酸克雷伯菌、大肠埃希菌和奇异变形杆菌。纸片扩散法的分类一致性（CA）和主要错误率是可以接受的。磷霉素对阴沟肠杆菌复合体和肺炎克雷伯菌的活性较低，其最低抑菌浓度（MIC50）等于大肠埃希菌 EUCAST 折点（8mg/L）。对于这些物种，三种替代技术高估了 MIC 和耐药性，不符合性能标准。对于肠杆菌科分离株的美西林检测，除奇异变形杆菌外，Etest ® 几乎符合 ISO 要求，纸片扩散法的 CA 率是可以接受的。VITEK ® 2 除了严重错误率过高外，也达到了测试产酸克雷伯菌和大肠埃希菌的 ISO 标准。对于奇异变形杆菌，无论使用哪种常规方法，其性能都是不可接受的。
市售检测方法可替代琼脂稀释法评估肠杆菌科尿路感染分离株对磷霉素（口服）和美西林的药敏性，但存在重要的种间变异性。需要更多包含更多磷霉素和美西林耐药分离株的研究来加强我们的结论。
