大肠埃希氏菌的qnrB基因检测与耐药机制研究

目的探索本地区医院大肠埃希氏菌喹诺酮耐药基因的分布及耐药机制。方法采用PCR扩增与测序、基因初步定位、质粒接合转移实验等方法确定喹诺酮耐药的大肠埃希氏菌qnr的基因类型,以分析研究有关的耐药特点与机制。结果各大肠埃希氏菌株中仅qnrB基因阳性,qnrA、qnrS、qnrC、qnrD、qepA、aac（6’）-Ib-cr基因均阴性;并且qnrB基因包括qnrB2、qnrB5、qnrB9、qnrB16、qnrB18、qnrB19和qnrB31等位基因;在这些qnrB等位基因中,qnrB31与qnrB16、qnrB2与qnrB9同源性较高;各qnrB等位基因分别位于约21.0 kb至28.0 kb长的质粒上。结论在本地区医院存在不同的qnrB等位基因流行;实验菌株的喹诺酮耐药与qnrB等位基因结构中LexA-蛋白结合位点共有序列缺失有关。

Detection of qnrB genes for Escherichia coli and study of resistance mechanisms

Objective To explore the distribution of quinolone resistant genes distribution in Escherichia coli isolates in hospital and resistance mechanisms in Escherichia coli. Methods Characteristics and mechanisms were analyzed for quinolone resistant qnr genes in Escherichia coli by PCR amplification and sequencing,gene mapping and plasmid conjugation experiments. Results Among various strains of Escherichia coli only qnrB gene was found positive; qnrA,qnrS,qnrC,qnrD,qepA,aac（6′）-Ib-cr genes were negative; and qnrB2,qnrB5,qnrB9,qnrB16,qnrB18,qnrB19 and qnrB31 alleles were found. Among these qnrB alleles,qnrB31 and qnrB16,qnrB2 and qnrB9 showed high homology.The qnrB alleles were found in the 21 kb to 28 kb long plasmids. Conclusions The prevalent of qnrB alleles were different among the local hospitals. Quinolone resistance of the experimental strain might be related to the deletion of the LeA- protein binding site of the qnrB gene.