耐碳青霉烯类抗菌药物大肠埃希菌耐药机制的研究

Research on the drug resistance mechanism of carbapenem-resistant Escherichia coli

目的了解河南省人民医院耐碳青霉烯类抗菌药物大肠埃希菌的耐药特点和耐药机制。方法收集临床送检合格样本分离到的细菌,采用BD Phoenix 100微生物分析系统进行细菌鉴定及体外药物敏感性分析,依照美国临床实验室标准化协会(CLSI)标准筛选出耐碳青霉烯类大肠埃希菌。采用改良Hodges和美罗培南(MEM)-乙二胺四乙酸(EDTA)-Na2双纸片协同试验进行表型筛选。聚合酶链反应(PCR)检测耐药基因blaKPC、blaNDM、blaVIM、blaIMP、blaOXA-48。对blaKPC阳性菌株进行接合转移试验。结果从1 238株大肠埃希菌中筛选到8株耐碳青霉烯类菌株,7株对亚胺培南(IPM)、MEM均耐药,有1株仅对MEM耐药。8株改良Hodges试验均为阳性,6株双纸片协同试验阳性。2株携带blaKPC-2,3株携带blaIMP-4。blaKPC-2可以发生接合转移。结论首次在河南省人民医院发现产blaIMP-4的大肠埃希菌,其耐碳青霉烯类抗菌药物的机制主要为携带blaKPC-2和blaIMP-4,blaKPC-2基因可以通过质粒水平传播。

Objective To investigate the drug resistance characteristics and mechanism of carbapenem-resistant Escherichia coli in Henan Provincial People＇s Hospital. Methods The identification and antimicrobial susceptibility in vitro of the isolates from qualified clinical specimens were analyzed by BD Phoenix 100 microorganism analysis system. The isolates of carbapenem-resistant Escherichia coli were screened according to the Clinical and Laboratory Standards Institute （ CLSI ） standard. Modified Hodges test and meropenem （ MEM ） -ethylene diamine tetraacetic acid （ EDTA ） -Na： double-disk synergy test were used for phenotypic screening of the isolates. By polymerase chain reaction （ PCR ） , the resistance genes, blarec, bla^Du, blazlu, bla^ue and blaoxa.48, in the isolates were detected. The transferability of blarec in the blar.Pc-positive isolates was studied by conjugation test. Results A total of 8 carbapenem-resistant Escherichia coli were screened from the 1 238 isolates. In the 8 isolates, 7 isolates were resistant to imipenem （ IPM ） and MEM, but 1 isolate was only resistant to MEM. All the 8 isolates were positive in the modified Hodges test, and 6 isolates were positive in the MEM-EDTA double-disk synergy test. There were 2 isolates carrying blaKec.2 and 3 isolates carrying bla1M,.4. Conjugation test indicated that blanc_2 could be transferred to Escherichia coli. Conclusions Carbapenem-resistant Escherichia coli carrying blazMe.4 is firstly reported in the hospital. The resistance mechanism of carbapenem-resistant Escherichia coli in the hospital is mainly carrying blakpc.2 and blaiMe.4, and the blarkPc-2 gene could be horizontally transmitted by plasmid.