Department of Internal Medicine, Medical School, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Infectious Diseases Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil; Laboratório de Pesquisa em Resistência Bacteriana (LABRESIS), Centro de Pesquisa Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
Laboratório de Pesquisa em Resistência Bacteriana (LABRESIS), Centro de Pesquisa Experimental, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil; Laboratório Weinmann-Grupo Fleury, Porto Alegre, Brazil.
J Glob Antimicrob Resist. 2020 Sep;22:40-42. doi: 10.1016/j.jgar.2020.02.006. Epub 2020 Feb 20.
Polymyxin resistance has been increasing in many regions, and appropriate determination of polymyxin susceptibility is now a major challenge worldwide. Many clinical laboratories rely on gradient diffusion methods to assess polymyxin susceptibility, although broth microdilution (BMD) is the only method currently recommended by the CLSI and EUCAST. The aim of this study was to assess the performance of the polymyxin B (PMB) Etest in a setting with a high prevalence of KPC-producing Klebsiella pneumoniae (KPC-KP).
A commercial Etest susceptibility testing method was evaluated and compared with the reference BMD method, considering isolates with a minimum inhibitory concentration (MIC) ≤2 mg/L for PMB as susceptible to this drug. A total of 310 clinical KPC-KP isolates were evaluated.
Susceptibility was significantly higher by Etest compared with BMD (82.6% vs. 75.8%). The MIC, MIC and modal MICs for PMB were 0.25, 32 and 0.25 mg/L (27.1%) by BMD and 0.5, 16 and 0.5 mg/L (49.7%) by Etest, respectively. Although categorical agreement was 90.0%, there was poor essential agreement (50.6%). A high rate (34.7%) of very major errors (VMEs) and a relatively low rate (2.1%) of major errors were found.
The considerable number of resistant isolates in this study allowed an accurate estimation of VME rates and, consequently, a more comprehensive assessment of susceptibility testing for polymyxins. Etest did not meet fully the acceptance criteria for US FDA requirements. These data do not support the use of this commercial method for determining PMB MICs in carbapenem-resistant Enterobacterales populations.
在许多地区，多粘菌素耐药性一直在增加，因此准确测定多粘菌素敏感性已成为全球范围内的主要挑战。许多临床实验室依赖梯度扩散法来评估多粘菌素敏感性，尽管肉汤微量稀释法（BMD）是 CLSI 和 EUCAST 目前唯一推荐的方法。本研究旨在评估高流行产 KPC 肺炎克雷伯菌（KPC-KP）地区中多粘菌素 B（PMB）E 试验的性能。
评估并比较了商业 E 试验药敏测试方法与参考 BMD 方法，考虑到 PMB 的最低抑菌浓度（MIC）≤2mg/L 的分离株对该药物敏感。共评估了 310 株临床 KPC-KP 分离株。
E 试验的药敏率明显高于 BMD（82.6%比 75.8%）。PMB 的 MIC、MIC 和模态 MIC 分别为 BMD 0.25、32 和 0.25mg/L（27.1%）和 Etest 0.5、16 和 0.5mg/L（49.7%）。虽然分类一致性为 90.0%，但基本一致性较差（50.6%）。发现非常大的错误（VME）发生率较高（34.7%），主要错误率相对较低（2.1%）。
本研究中大量的耐药分离株使 VME 率的准确估计成为可能，从而更全面地评估多粘菌素的药敏测试。E 试验未完全满足美国 FDA 要求的接受标准。这些数据不支持使用该商业方法来确定碳青霉烯类耐药肠杆菌科人群中的 PMB MIC。
