Department of Microbiology, Medical School, University of Athens, Athens, Greece.
J Antimicrob Chemother. 2010 Aug;65(8):1664-71. doi: 10.1093/jac/dkq210. Epub 2010 Jun 11.
The increasing frequency of class A KPC enzymes and class B metallo-beta-lactamases (MBLs) among Enterobacteriaceae as well as their possible co-production makes their early differentiation urgent.
A simple phenotypic algorithm employing three combined-disc tests consisting of meropenem alone and with phenylboronic acid (PBA), EDTA, or both PBA and EDTA was designed for the differentiation of KPC and MBL enzymes. Augmentation of the zone of inhibition by >or=5 mm was considered a positive combined-disc test result. A total of 141 genotypically confirmed carbapenemase-positive Enterobacteriaceae clinical isolates (63 KPC producers, 47 MBL producers, and 31 KPC and MBL producers) with various carbapenem MICs were examined. For comparison, 84 genotypically confirmed carbapenemase-negative Enterobacteriaceae clinical isolates [39 extended-spectrum beta-lactamase (ESBL) producers, 22 AmpC producers, and 23 ESBL and AmpC producers] were also tested.
The phenotypic algorithm was able to differentiate MBL from KPC producers as well as to detect the possible co-production of both carbapenemases (positive result only with the combined-disc test using meropenem alone and with both PBA and EDTA). The method detected all KPC or MBL producers (sensitivity 100%) as well as 30 of the KPC and MBL producers (sensitivity 96.8%). All three combined-disc tests were negative for non-carbapenemase-producing isolates, except two ESBL and AmpC producers that gave positive combined-disc tests using meropenem alone and with PBA and both PBA and EDTA (specificity for KPC detection 98.8%).
This phenotypic method is very helpful to detect carbapenemase production and provides a simple algorithm for the differentiation of KPC and MBL enzymes, especially in regions where KPC- and MBL-possessing Enterobacteriaceae are highly prevalent.
肠杆菌科中 A 类 KPC 酶和 B 类金属β-内酰胺酶（MBLs）的频率不断增加，以及它们可能的共同产生，使得对它们进行早期区分变得尤为迫切。
设计了一种简单的表型算法，该算法使用三个组合圆盘试验，包括单独使用美罗培南以及联合使用苯硼酸（PBA）、乙二胺四乙酸（EDTA）或 PBA 和 EDTA。如果抑制带的宽度增加>或=5 毫米，则被认为是阳性组合圆盘试验结果。共检测了 141 株经基因确证的产碳青霉烯酶的肠杆菌科临床分离株（63 株 KPC 产生菌、47 株 MBL 产生菌和 31 株 KPC 和 MBL 产生菌），这些分离株的各种碳青霉烯 MIC 不同。为了比较，还检测了 84 株经基因确证的产碳青霉烯酶阴性的肠杆菌科临床分离株（39 株超广谱β-内酰胺酶（ESBL）产生菌、22 株 AmpC 产生菌和 23 株 ESBL 和 AmpC 产生菌）。
表型算法能够区分 MBL 和 KPC 产生菌，并且能够检测出两种碳青霉烯酶的可能共同产生（仅使用单独的美罗培南以及联合使用 PBA 和 EDTA 的组合圆盘试验呈阳性结果）。该方法能够检测到所有的 KPC 或 MBL 产生菌（敏感性为 100%）以及 30 株 KPC 和 MBL 产生菌（敏感性为 96.8%）。除了 2 株同时使用单独的美罗培南、PBA 和 PBA 和 EDTA 进行组合圆盘试验呈阳性的 ESBL 和 AmpC 产生菌外，所有三种组合圆盘试验对非产碳青霉烯酶的分离株均呈阴性（KPC 检测的特异性为 98.8%）。
这种表型方法非常有助于检测碳青霉烯酶的产生，并提供了一种简单的算法，用于区分 KPC 和 MBL 酶，特别是在存在大量携带 KPC 和 MBL 的肠杆菌科的地区。
