Performance of polymyxin B Etest in a setting of high prevalence of KPC-producing Klebsiella pneumoniae. (September 2020)

• Record Type: Journal Article
• Authors: Zavascki, Alexandre P.; Magagnin, Cibele Massotti; Wink, Priscila Lamb; de Oliveira, Vanessa Pimentel; Nunes, Aline Gabrielle; Krummer, Thaysa Guglieri; Aquino, Valério Rodrigues; Barth, Afonso Luís
• Is Part Of: Journal of global antimicrobial resistance. Volume 22(2020)
• Page Start: 40
• Page End: 42
• Publication Date: 2020-09
• Subjects: Broth microdilution -- Carbapenem resistance -- Colistin -- Gradient test -- Klebsiella pneumoniae -- Polymyxin B; Drug resistance -- Periodicals; Drug resistance -- Periodicals; Drug resistance; Periodicals; 616.9041
• DOI: 10.1016/j.jgar.2020.02.006
• Languages: English
• ISSNs: 2213-7165

Abstract

Highlights: Susceptibility of 310 clinical KPC- KP by Etest and reference BMD was compared. The results showed an unacceptably high rate of very major errors (34.7%). Etest did not fully meet the acceptance criteria for FDA requirements. Abstract: Objectives: 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). Methods: 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. Results: Susceptibility was significantly higher by Etest compared with BMD (82.6% vs. 75.8%). The MIC50, MIC90 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. Conclusion: 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.