Department of Laboratory Medicine, Gyeongsang National University Hospital, Gyeongsang National University College of Medicine, (52727) 79 Gangnam-ro, Jinju, Gyeongnam, South Korea.
Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Severance Hospital, Yonsei University College of Medicine, (03722) 50-1 Yonsei-ro, Seodaemun-gu, Seoul, South Korea.
J Microbiol Methods. 2020 Jan;168:105781. doi: 10.1016/j.mimet.2019.105781. Epub 2019 Nov 20.
Detecting carbapenemase-producing Enterobacteriaceae (CPE) has become increasingly difficult due to the emergence of diverse enzymes. The aim of the study was to evaluate an agar plate-based modified carbapenem inactivation method (p-mCIM) for detection of CPE. Stock strains and clinical isolates of CPE were used to evaluate the p-mCIM. The p-mCIM was performed as described for the mCIM, except that meropenem disks were placed on the lawn of test organisms on Mueller-Hinton agar (MHA) plates. Among 17 stock strains of CPE, six of eight KPC-2-like- and all six NDM-1-like carbapenemase-producing strains were positive by the p-mCIM without incubation in the carbapenem inactivation (CI) step. Among 380 CPE clinical isolates detected, 308 and 38 were KPC-2-like and NDM-1-like enzyme producers, respectively. The required incubation time in the CI step to show all isolates were positive by p-mCIM was 3 h for isolates with KPC-2-like enzyme and 1 h for isolates with metallo-β-lactamases. Twenty-eight of 30 isolates with OXA-48-like enzymes were p-mCIM positive. Sensitivities of both the p-mCIM and the mCIM (based on inhibition zone of ≤15 mm) for detection of CPE were 100%. All 70 ertapenem-nonsusceptible, but carbapenemase gene-negative isolates tested were both p-mCIM (based on inhibition zone of ≥21 mm) and mCIM negative. In conclusion, performance of the p-mCIM, which uses a lawn of bacterial colonies on MHA plate instead of a bacteria-suspended Tryptic soy broth tube in the CI step, is essentially identical to that of the CLSI-recommended mCIM in the detection of clinical isolates of Enterobacteriaceae producing carbapenemases including difficult to detect bla-like enzymes.
由于不同酶的出现，检测产碳青霉烯酶肠杆菌科（CPE）变得越来越困难。本研究旨在评估琼脂平板改良碳青霉烯失活法（p-mCIM）检测 CPE 的性能。使用 CPE 的标准株和临床分离株来评估 p-mCIM。p-mCIM 的操作方法与 mCIM 相同，只是在 Mueller-Hinton 琼脂（MHA）平板上的测试菌菌落在用美罗培南纸片孵育前，将美罗培南纸片放在菌落上。在 17 株 CPE 标准株中，6 株 KPC-2 样和 6 株 NDM-1 样碳青霉烯酶产生株在无需碳青霉烯失活（CI）步骤孵育的情况下，p-mCIM 阳性。在 380 株 CPE 临床分离株中，308 株和 38 株分别为 KPC-2 样和 NDM-1 样酶产生株。CI 步骤中使所有分离株通过 p-mCIM 呈阳性所需的孵育时间对于 KPC-2 样酶的分离株为 3 小时，对于金属β-内酰胺酶的分离株为 1 小时。28 株 OXA-48 样酶的分离株 p-mCIM 阳性。p-mCIM 和 mCIM（基于抑制圈≤15mm）检测 CPE 的敏感性均为 100%。所有 70 株厄他培南不敏感但碳青霉烯酶基因阴性的分离株 p-mCIM（基于抑制圈≥21mm）和 mCIM 均为阴性。总之，p-mCIM 的性能与 CLSI 推荐的 mCIM 基本相同，它使用 MHA 平板上的细菌菌落菌落在 CI 步骤中代替细菌悬浮在 Tryptic soy broth 管中，用于检测包括难以检测 bla 样酶在内的产碳青霉烯酶肠杆菌科的临床分离株。
