Department of Medical Microbiology, Academic Medical Center, Amsterdam, The Netherlands; Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Clin Microbiol Infect. 2014 Apr;20(4):345-9. doi: 10.1111/1469-0691.12322. Epub 2013 Aug 9.
Class A and B carbapenemases in Enterobacteriaceae may be detected using carbapenemase inhibition tests with boronic acid derivatives (BA) and dipicolinic acid (DPA)/EDTA, respectively. However, for OXA-48 (like) carbapenemases, no specific inhibitor is available. Because OXA-48 confers high-level temocillin resistance, a disc diffusion assay using temocillin as well as BA and DPA inhibition tests was evaluated for detection of class A, B and OXA-48 carbapenemases. The test collection included 128 well-characterized non-repeat Enterobacteriaceae isolates suspected of carbapenemase production; that is, with meropenem MICs ≥ 0.5 mg/L, including 99 carbapenemase producers (36 KPC, one GES, 31 MBL, four KPC plus VIM, 25 OXA-48, two OXA-162), and 29 ESBL and/or AmpC-producing isolates. PCR and sequencing of beta-lactamase genes was used as a reference test. Phenotypic carbapenemase detection was performed with discs (Rosco) containing meropenem (10 μg), temocillin (30 μg), meropenem + phenyl boronic acid (PBA), meropenem + DPA, meropenem + BA + DPA, and meropenem + cloxacillin (CL). Absence of synergy between meropenem and BA and/or DPA and a temocillin zone ≤10 mm was used to identify OXA-48. The sensitivity for identification of class A, B and OXA-48 carbapenemases was 95%, 90% and 100%, with 96-100% specificity. In non-Proteus species, the sensitivity for class B carbapenemase detection was 97%. All isolates without PBA or DPA synergy and a temocillin disc zone ≤10 mm were OXA-48 (like) positive. In conclusion, carbapenemase inhibition tests with PBA and DPA combined with a temocillin disc provide a reliable phenotypic confirmation method for class A, B and OXA-48 carbapenemases in Enterobacteriaceae.
A 类和 B 类碳青霉烯酶可以使用硼酸盐衍生物 (BA) 和二吡啶酸 (DPA)/EDTA 分别进行碳青霉烯酶抑制试验检测。然而，对于 OXA-48（类）碳青霉烯酶，没有可用的特定抑制剂。由于 OXA-48 赋予了高水平的替莫西林耐药性，因此评估了使用替莫西林以及 BA 和 DPA 抑制试验的纸片扩散法来检测 A、B 和 OXA-48 碳青霉烯酶。试验集包括 128 株经过充分鉴定的非重复肠杆菌科分离株，这些分离株疑似产生碳青霉烯酶；即，美罗培南 MIC 为 ≥0.5mg/L，包括 99 株碳青霉烯酶产生菌（36 株 KPC、1 株 GES、31 株 MBL、4 株 KPC 加 VIM、25 株 OXA-48、2 株 OXA-162）和 29 株 ESBL 和/或 AmpC 产生菌。使用β-内酰胺酶基因的 PCR 和测序作为参考试验。使用含有美罗培南（10μg）、替莫西林（30μg）、苯硼酸（PBA）、DPA、BA+DPA 和 cloxacillin（CL）的纸片（Rosco）进行表型碳青霉烯酶检测。如果美罗培南与 BA 和/或 DPA 之间没有协同作用，并且替莫西林纸片的抑菌圈直径≤10mm，则用于鉴定 OXA-48。鉴定 A、B 和 OXA-48 碳青霉烯酶的灵敏度为 95%、90%和 100%，特异性为 96-100%。在非变形杆菌属物种中，B 类碳青霉烯酶检测的灵敏度为 97%。所有没有 PBA 或 DPA 协同作用且替莫西林纸片抑菌圈直径≤10mm 的分离株均为 OXA-48（类）阳性。总之，使用 PBA 和 DPA 进行碳青霉烯酶抑制试验，结合替莫西林纸片，为肠杆菌科中 A、B 和 OXA-48 碳青霉烯酶提供了一种可靠的表型确证方法。
