School of Medicine, University College Dublin, Belfield, Dublin 4, Ireland; Department of Clinical Microbiology, St Vincent's University Hospital, Elm Park, Dublin D04 T6F4, Ireland.
School of Public Health, Physiotherapy & Sports Science, University College Dublin, Belfield, Dublin D04 N2E5, Ireland.
J Glob Antimicrob Resist. 2021 Dec;27:284-288. doi: 10.1016/j.jgar.2021.09.010. Epub 2021 Nov 12.
IMP-type carbapenemases are rarely detected in Europe and limited information is available to guide the treatment of infections caused by carbapenemase-producing Enterobacterales (CPE) producing these carbapenemases. Accurate antimicrobial susceptibility testing (AST) results are essential for optimal antibiotic management. Here we report discrepancies in AST of IMP-producing Enterobacterales (IMP-CPE) complicating the management of severe sepsis.
Antimicrobial susceptibilities were analysed by in-house VITEK® 2, Etest and broth microdilution (BMD). Carbapenemase-encoding genes were detected by PCR. Whole-genome sequencing (WGS) was performed using an Illumina MiSeq platform.
Minimum inhibitory concentrations (MICs) determined by VITEK® 2 for Enterobacter hormaechei and Klebsiella oxytoca blood culture isolates were ≥16 mg/L for meropenem and ≤0.5 mg/L for ertapenem. In contrast, Etest analysis and BMD returned MICs of 2 mg/L and 1 mg/L, respectively. Both isolates tested positive for IMP carbapenemase-encoding genes by PCR. WGS revealed that both isolates carried the same bla gene. Based on VITEK® 2 susceptibilities, initial treatment was with tigecycline and amikacin. After subsequent deterioration, the patient was successfully treated with ertapenem and amikacin.
This case highlights that automated AST by VITEK® 2 can over-report meropenem resistance for IMP carbapenemase-producers compared with Etest and BMD. Clinicians need to be cautious deciding against carbapenem treatment based on VITEK® 2 susceptibility testing results for IMP-positive Enterobacterales. Tigecycline was inferior to carbapenem treatment for pyelonephritis caused by isolates expressing IMP carbapenemases, however specific evidence guiding the treatment of these infections is lacking.
IMP 型碳青霉烯酶在欧洲很少被检出，关于如何治疗产这些碳青霉烯酶的肠杆菌科细菌（CPE）感染，相关信息有限。准确的抗菌药物敏感性测试（AST）结果对于优化抗生素管理至关重要。本研究报告了产 IMP 肠杆菌科细菌（IMP-CPE）的 AST 差异，这些差异使严重脓毒症的管理变得复杂。
采用 VITEK® 2、Etest 和肉汤微量稀释法（BMD）进行抗菌药物敏感性分析。采用 PCR 检测碳青霉烯酶编码基因。采用 Illumina MiSeq 平台进行全基因组测序（WGS）。
VITEK® 2 测定 Enterobacter hormaechei 和 Klebsiella oxytoca 血培养分离株对美罗培南的 MIC 为≥16 mg/L，对厄他培南的 MIC 为≤0.5 mg/L。相比之下，Etest 分析和 BMD 分别返回 MIC 值为 2 mg/L 和 1 mg/L。PCR 均检测到这两种分离株均携带 IMP 碳青霉烯酶编码基因。WGS 显示两种分离株均携带相同的 bla 基因。根据 VITEK® 2 的药敏结果，初始治疗方案为替加环素和阿米卡星。随后病情恶化，改用厄他培南和阿米卡星治疗后，患者痊愈。
本案例表明，与 Etest 和 BMD 相比，VITEK® 2 自动化 AST 可能会过高报告 IMP 碳青霉烯酶生产者对美罗培南的耐药性。临床医生在根据 IMP 阳性肠杆菌科细菌的 VITEK® 2 药敏结果决定不使用碳青霉烯类药物治疗时需要谨慎。替加环素对表达 IMP 碳青霉烯酶的分离株引起的肾盂肾炎的疗效不如碳青霉烯类药物，但缺乏针对这些感染治疗的具体证据。
