Servicio Antimicrobianos, Departamento Bacteriología, Instituto Nacional de Enfermedades Infecciosas-ANLIS Dr Carlos G. Malbrán, Ministerio de Salud y Ambiente, Ciudad Autónoma de Buenos Aires, Argentina.
J Clin Microbiol. 2010 Apr;48(4):1323-32. doi: 10.1128/JCM.01771-09. Epub 2010 Feb 24.
The modified Hodge method (MHT) has been recommended by the CLSI for confirmation of suspected class A carbapenemase production in species of Enterobacteriaceae. This test and the Masuda method (MAS) have advantages over traditional phenotypic methods in that they directly analyze carbapenemase activity. In order to identify the potential interferences of these tests, we designed a panel composed of diverse bacterial genera with distinct carbapenem susceptibility patterns (42 carbapenemase producers and 48 nonproducers). About 25% of results among carbapenemase nonproducers, mainly strains harboring CTX-M and AmpC hyperproducers, were observed to be false positive. Subsequently, we developed an optimized approach for more-accurate detection of suspicious isolates of carbapenemase by addition of boronic acid (BA) derivatives (reversible inhibitor of class A carbapenemases and AmpC cephalosporinases) and oxacillin (inhibitor of AmpCs enzymes). The use of the modified BA- and oxacillin-based MHT and MAS resulted in high sensitivity (>90%) and specificity (100%) for class A carbapenemase detection. By use of these methodologies, isolates producing KPCs and GES, Sme, IMI, and NMC-A carbapenemases were successfully distinguished from those producing other classes of ss-lactamases (extended-spectrum beta-lactamases [ESBLs], AmpC beta-lactamases, metallo-beta-lactamases [MBLs], etc.). These methods will provide the fast and useful information needed for targeting of antimicrobial therapy and appropriate infection control.
改良 Hodge 法（MHT）已被 CLSI 推荐用于确认肠杆菌科中疑似 A 类碳青霉烯酶产生的情况。与传统表型方法相比，该测试和 Masuda 法（MAS）具有优势，因为它们直接分析碳青霉烯酶活性。为了确定这些测试的潜在干扰，我们设计了一个由具有不同碳青霉烯敏感性模式的不同细菌属组成的面板（42 个碳青霉烯酶产生者和 48 个非产生者）。在碳青霉烯酶非产生者中，约 25%的结果观察到为假阳性，主要是携带 CTX-M 和 AmpC 超产的菌株。随后，我们开发了一种优化方法，通过添加硼酸（BA）衍生物（A 类碳青霉烯酶和 AmpC 头孢菌素酶的可逆抑制剂）和苯唑西林（AmpC 酶抑制剂），更准确地检测可疑的碳青霉烯酶分离株。改良的 BA 和苯唑西林基础 MHT 和 MAS 的使用导致 A 类碳青霉烯酶检测的灵敏度（>90%）和特异性（100%）较高。使用这些方法学，成功区分了产生 KPCs 和 GES、Sme、IMI 和 NMC-A 碳青霉烯酶的分离株与产生其他类别的 ss-内酰胺酶（扩展谱β-内酰胺酶 [ESBLs]、AmpC 内酰胺酶、金属β-内酰胺酶 [MBLs]等）的分离株。这些方法将为靶向抗菌治疗和适当的感染控制提供快速有用的信息。
