Findlay Jacqueline, Hopkins Katie L, Meunier Daniele, Woodford Neil
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, Public Health England, London NW9 5EQ, UK.
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, Public Health England, London NW9 5EQ, UK
J Antimicrob Chemother. 2015 May;70(5):1338-42. doi: 10.1093/jac/dku571. Epub 2015 Jan 27.
To assess the performance of three commercial molecular assays for detecting major families of carbapenemases in pure bacterial isolates.
A panel of 450 isolates with previously defined carbapenem resistance mechanisms was tested using the Check-Direct CPE kit, the eazyplex(®) SuperBug complete A kit and the Xpert(®) Carba-R kit. Isolates included 438 Enterobacteriaceae and 12 Pseudomonas spp. comprising 100 isolates each with KPC, NDM, VIM or OXA-48-like enzymes, two isolates producing both an NDM and an OXA-48-like enzyme, 24 IMP producers and 24 isolates without a known carbapenemase gene. Discordant results (commercial versus in-house) were investigated using in-house PCR and amplicons were sequenced to define the carbapenemase allele present.
All three commercial assays detected all isolates with KPC, VIM, NDM and classic OXA-48 carbapenemases (no false-negatives). Isolates producing the OXA-181 variant (n = 18) were not detected by the Xpert(®) Carba-R kit or the eazyplex(®) SuperBug complete A kit, but were subsequently detected with modified versions of these kits. Only the Xpert(®) Carba-R kit could detect IMP carbapenemases, although this was limited to the IMP-1 subgroup. Invalid or false-positive results were either not observed when following the manufacturer's protocols or were eliminated by making simple interpretative adjustments to allow use with bacterial isolates rather than clinical samples.
Commercial assays offer a reliable means of detecting bacteria with clinically significant carbapenemases. Coverage of some assays required expansion to maximize the sensitivity for OXA-48-like carbapenemases. Choice will ultimately depend on preferred gene coverage, intended throughput, cost and ability to fit into local workflows.
评估三种商业分子检测方法在检测纯细菌分离株中主要碳青霉烯酶家族方面的性能。
使用Check-Direct CPE试剂盒、eazyplex(®) SuperBug complete A试剂盒和Xpert(®) Carba-R试剂盒对一组450株先前已确定碳青霉烯耐药机制的分离株进行检测。分离株包括438株肠杆菌科细菌和12株假单胞菌属细菌，其中分别有100株携带KPC、NDM、VIM或OXA-48样酶，2株同时产生NDM和OXA-48样酶，24株产IMP酶，以及24株无已知碳青霉烯酶基因的分离株。对不一致的结果（商业检测方法与内部检测方法）使用内部PCR进行研究，并对扩增子进行测序以确定存在的碳青霉烯酶等位基因。
所有三种商业检测方法均检测到了所有携带KPC、VIM、NDM和经典OXA-48碳青霉烯酶的分离株（无假阴性）。Xpert(®) Carba-R试剂盒或eazyplex(®) SuperBug complete A试剂盒未检测到产生OXA-181变体的分离株（n = 18），但随后使用这些试剂盒的改良版本检测到了。只有Xpert(®) Carba-R试剂盒能够检测IMP碳青霉烯酶，不过这仅限于IMP-1亚组。按照制造商的方案操作时，未观察到无效或假阳性结果，或者通过进行简单的解释性调整以允许用于细菌分离株而非临床样本，从而消除了这些结果。
商业检测方法为检测携带具有临床意义的碳青霉烯酶的细菌提供了一种可靠的手段。某些检测方法的覆盖范围需要扩大，以最大限度地提高对OXA-48样碳青霉烯酶的敏感性。最终的选择将取决于首选的基因覆盖范围、预期的通量、成本以及适应本地工作流程的能力。
