某医院CTX-M型超广谱β-内酰胺酶的分子流行病学研究

目的了解某医院产CTX-M型超广谱β-内酰胺酶(ESBLs)的大肠埃希菌、肺炎克雷伯菌和阴沟肠杆菌检出率,确定其基因型,并对其相关流行病学进行研究。方法收集2004年10月—2005年7月医院临床标本分离的多重耐药大肠埃希菌、肺炎克雷伯菌和阴沟肠杆菌134株,按美国临床实验室标准化研究所(CLSI/NC-CLS)所推荐的方法进行表型确证试验,以聚合酶链反应(PCR)法进一步检测CTX-M酶基因型,PCR产物测序并确定其基因型。随机扩增多态DNA(RAPD)对携带CTX-M酶的阳性菌株作流行病学分析。结果112株ESBLs表型阳性的肠杆菌科细菌中90株携带CTX-M基因,共检出3种基因型,即CTX-M-15、CTX-M-3和CTX-M-14。RAPD共测40株菌,19株大肠埃希菌有7种RAPD类型,11株肺炎克雷伯菌有5种RAPD类型,10株阴沟肠杆菌有7种RAPD类型。结论肠杆菌科细菌产CTX-M型ESBLs相当普遍,主要为CTX-M-15、CTX-M-3和CTX-M-14。CTX-M酶存在克隆传播。

Study on molecular epidemiology of CTX-M type extended-spectrum β-lactamases in a hospital

Objective To investigate the prevalence of CTX-M-producing Escherichia coli,Klebsiella pneumonia and Enterobacter cloacae isolates in a hospital,and to identify the subtype of CTX-M encoding genes and study the epidemiological characteristics of CTX-M-producing isolates.Methods One hundred and thirty-four clinical strains of above multi-resistant Escherichia coli,Klebsiella pneumonia and Enterobacter cloacae isolates were collected from Xiangya Hospital from October 2004 to July 2005.ESBLs-producing isolates were confirmed by phenotypic confirmatory tests as recommended by the CLSI/NCCLS,PCR and DNA sequencing were used to determine the genotype of the CTX-M enzymes.The homology of CTX-M-producing strains were detected by randomly amplified polymorphic DNA(RAPD) typing method.Results Ninety of 112 ESBLs-producing Enterobacteriaceae isolates were confirmed to produce CTX-M genes by multiplex PCR.The subtypes of CTX-M enzymes were CTX-M-15,CTX-M-3 and CTX-M-14.There were 7 RAPD types in 19 isolates of CTX-M-producing Escherichia coli,5 types in 11 isolates of CTX-M-producing Klebsiella pneumoniae,7 types in 10 isolates of CTX-M-producing Enterobacter cloacae.Conclusion CTX-M-producing Enterobacteriaceae is common.the main subtypes are CTX-M-15,CTX-M-3 and CTX-M-14.Clone spread has played a certain role in CTX-M enzymes dissemination.