5株携带blaNDM-5基因大肠埃希菌临床株的分子流行特征分析

Molecular epidemiology of 5 clinical isolates of Escherichia coli harboring blaNDM-5 gene

目的探讨耐碳青霉烯类抗菌药物大肠埃希菌的耐药机制并对分离株的分子流行特征进行分析,为医院感染的防控提供依据。方法选取2015年5月-2016年10月住院患者标本分离的5株耐碳青霉烯类抗菌药物的大肠埃希菌,产金属碳青霉烯酶的筛选采用亚胺培南/EDTA复合E-test条,采用PCR方法检测菌株携带的碳青霉烯酶、超广谱β-内酰胺酶、ampC酶和喹诺酮类耐药相关基因,并测序确认类型及其亚型,脉冲场凝胶电泳技术检测分离株间的同源性,液相质粒接合试验分析质粒的转移特性。结果除了阿米卡星和氨曲南外,5株大肠埃希菌对目前测试的头孢菌素、碳青霉烯类和喹诺酮类抗菌药物都耐药,且金属酶表型实验结果都呈现阳性;5株大肠埃希菌携带不同的耐药基因,但都携带blaNDM-5和blaTEM-1基因;脉冲场凝胶电泳显示5株大肠埃希菌的脉冲带型不一致,没有呈现克隆聚集性;质粒接合试验没有显示5株大肠埃希菌临床株(供体菌)将携带blaNDM-5的质粒转移到大肠埃希菌J53AziR(受体菌)。结论研究结果表明本地区存在携带blaNDM-5基因的大肠埃希菌的流行,但没有呈现克隆聚集暴发性,为预防和控制医院感染的暴发,必须重视和加强对耐碳青霉烯类抗菌药物肠杆菌的监测。

OBJECTIVE To explore the drug resistance mechanisms of carbapenemase-resistant Escherichia coli strains and analyze the molecular epidemiology of the clinical isolates so as to provide guidance for prevention and control of nosocomial infections.METHODS Totally 5 strains of carbapenemase-resistant E.coli were isolated from the specimens that were obtained from the patients who were hospitalized from May 2015 to Oct 2016,the strains that produced metallo-beta-lactamases（MBL）were screened by using imipenem/EDTA E-tests.The antimicrobial resistance genes encoding extended-spectrum β-lactamases（EBSLs）,plasmid ampC-type,cabapenemases and quinolones were determined by polymerase-chain-reaction（PCR）and confirmed by sequencing,the clonal related-ness were identified with the use of pulsed-field gel electrophoresis（PFGE）,and the transferability of plasmids was analyzed by means of liquid phase plasmid conjugation test.RESULTS The 5 isolates were resistant to all of the tested antibiotics cephalosporins,carbapenems and quinolones except for aztreonam and amikacin and showed posi-tive for MBL phenotype test.The 5 E.coli isolates harbored different drug resistance genes,but all of them har-bored blaNDM-5 and blaTEM-1 genes.The PFGE indicated that the 5 isolates were categorized into five types be-ing unrelated strains and did not show clonal aggregation.The plasmid conjugation test showed that the 5 E.coli i-solates（donor strains）did not transfer from the blaNDM-5 plasmid to E.coli J53AziR（recipient strain）.CONCLUSION It is concluded that the E.coli strains harboring the blaNDM-5 gene are prevalent in this area but do not show the clonal aggregation.It is necessary to attach great importance to the surveillance of carbapenemase-resistant Enterobacter so as to prevent and control the nosocomial infections.