MHT和mCIM试验检测肠杆菌科金属碳青霉烯酶效能的评价

Evaluation on MHT and mCIM for detection of carbapenemase in Enterobacteriaceae

目的探讨改良Hodge试验(MHT)及改良碳青霉烯灭活试验(mCIM)检测肠杆菌科细菌金属碳青霉烯酶的应用价值。方法 VITEK 2Compact全自动细菌鉴定及药敏系统进行细菌鉴定和药敏试验,筛选2015-2017年非重复临床分离的碳青霉烯类耐药的肠杆菌科细菌,MHT及mCIM进行产碳青霉烯酶表型确证试验,PCR检测常见的金属碳青霉烯酶IMP-4、IMP-8、VIM-1、VIM-2、NDM基因。比较MHT及mCIM对肠杆菌科金属碳青霉烯酶的检测效能。结果本实验共收集40株临床分离菌株,MHT阳性36株,阳性率90.0%。mCIM阳性39株,阳性率为97.5%。PCR产物测序Blast比对证实4株为产IMP酶菌株,5株产NDM型菌株,未检测到VIM基因。MHT试验检测IMP酶的灵敏度、特异性、阳性预测值、阴性预测值分别为100.0%、11.1%、11.1%、100.0%,MHT检测NDM酶分别为40.0%、2.9%、5.6%、25.0%。mCIM检测IMP酶的灵敏度、特异性、阳性预测值、阴性预测值分别100.0%、2.8%、10.3%、100.0%,mCIM检测NDM型分别为100.0%、2.9%、12.8%、100.0%。结论 MHT及mCIM检测肠杆菌科细菌产金属碳青霉烯酶具有良好的灵敏度,但特异性偏低,应结合分子生物学方法进行检测,为感染控制提供保障。

Objective To investigate the application value of modified Hodge test（MHT）and modified carbapenem inactivation method（mCIM）for detection of metallo-carbapenemase in Enterobacteriaceae.Methods VITEK 2 Compact automatic analysis system was used to identify and test the drug sensitivity of non-repeated strains of carbapenem-resistant Enterobacteriaceae（CRE）isolated during 2015-2017.MHT and mCIM were conducted to confirm the phenotypes of carbapenemases,and PCR was used to detect common IMP-4,IMP-8,VIM-1,VIM-2 and NDM genes.The performances of MHT and mCIM in the detection of metallo-carbapenemases were compared.Results A total of 40 clinical isolates were detected.Among which 36 isolates（90.0%） were positive by MHT,while 39 isolates（97.5%） were positive by mCIM.Sequencing of PCR products and Blast confirmed that 4 strains were IMP producing strains while 5 strains were NDM producing strains;no VIM positive strains were detected.The sensitivity,specificity,positive predictive value and negative predictive value of MHT for IMP were 100.0%,11.1%,11.1% and100.0% respectively,while those for NDM were 40.0%,2.9%,5.6% and 25.0% respectively.The sensitivity,specificity,positive predictive value and negative predictive value of mCIM for IMP were 100.0%,2.8%,10.3% and 100.0% respectively,while those for NDM were 100.0%,2.9%,12.8% and100.0% respectively.Conclusion MHT and mCIM have a good sensitivity for the detection of metallo-carbapenemases in Enterobacteriaceae,but the specificity is low.It is better to use them in combination with molecular biology methods to provide guaranteed results.