临床来源碳青霉烯耐药大肠埃希菌药物敏感性及分子流行病学特征分析

Drug susceptibility and molecular epidemiological characteristics of clinical isolates of carbapenem-resistant Escherichia coli

目的探讨临床分离的碳青霉烯耐药大肠埃希菌药物敏感性特征及分子流行病学特征,为院内感染控制及临床治疗提供基础数据。方法收集某医院临床分离的21株对碳青霉烯类药物耐药的大肠埃希菌,采用琼脂稀释法测定菌株对11种临床常用药物的最低抑菌浓度(MIC);Carba NP试验检测菌株产碳青霉烯酶情况;采用PCR扩增及序列比对检测耐药基因(包括bla_(NDM)、bla_(KPC)、bla_(IMP)、bla_(VIM)、bla_(OXA))携带状况;采用脉冲场凝胶电泳(PFGE)和多位点序列分型(MLST)对菌株进行分子分型。结果 21株碳青霉烯耐药大肠埃希菌中,对哌拉西林、头孢吡肟、头孢曲松、头孢他啶等β-内酰胺类药物和左氧氟沙星耐药率为100.00%;对甲氧苄啶-磺胺甲恶唑的耐药率也高达76.19%;对米诺环素、阿米卡星和磷霉素的耐药率相对较低,分别为23.81%、23.81%和19.05%。Carba NP试验阳性菌株17株,均携带bla_(NDM-1)基因,其余4种基因检测均为阴性。MLST显示21株菌株共有9种ST型别,其中携带bla_(NDM-1)基因的大肠埃希菌主要为ST167型和ST540型。PFGE显示来自泌尿外科的3株菌株电泳图谱完全相同,另外来自不同病房的2株菌株电泳图谱也完全相同,提示医院内存在同一克隆菌株传播的可能。结论该医院碳青霉烯耐药大肠埃希菌基因型分布呈现多态性;对碳青霉烯类药物耐药的机制主要是携带bla_(NDM-1)基因;携带该基因的大肠埃希菌对临床常用抗菌药物往往呈现多重耐药,给临床治疗带来了困难。加强对碳青霉烯耐药菌株基因型和耐药基因的检测,将对减缓或阻断耐药菌的传播具有重要意义。

Objective To explore the drug susceptibility and molecular epidemiological characteristics of clinical isolates of carbapenem-resistant Escherichia coli. Methods A total of 21 carbapenem-resistant E. coli strains were isolated from a hospital in 2015. The minimum inhibitory concentration （MIC） of these strains were detected by agar dilution method. Carba NP test was used to detect carbapenemases. Carbapenemase genes including blaNDM, blaKPC, blaIMP, blaVIM and blaoxg were detected by PCR followed by sequence alignment; Pulsed-field gel electrophoresis （PFGE） and multi locus sequence typing （MLST） were performed for the molecular subtyping. Results All the 21 carbapenem-resistant E. coli strains were resistant to imipenem, meropenem, piperacillin, cefepime, ceftriaxone, ceftazidime and levofloxacin. The resistant rate to trimethoprim- sulfamethoxazole was as high as 76. 19%. The resistant rates to minocycline, amikacin and fosfomycin were 23.81%, 23.81% and 19. 05%, respectively. Seventeen strains were positive in Carba NP test. PCR and sequences alignment confirmed that the 17 strains carried blaNDM.1 genes. The other four carbapenemase genes were not detected. MLST analysis showed that 21 strains could be divided into nine ST types, ST167 and ST540 were detected in the strains carrying blaNDM-1. Three strains from a urology ward had identical PFGE patterns and another two strains from different wards also had identical patterns, suggesting the spread of an E. coli clone in the ward. Condusion blaNDM-1 gene was carried by E. coli strains with different ST types in the hospital. E. coli strains carrying the blaNDM-1 were highly resistant to common antimicrobial drugs. It is important to strengthen thedetection and surveillance of transmission of E. coli strains carrying blaNDM-1 gene in hospitals.