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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。
Objective To explore the distribution and mechanism of quinolone resistance genes of Escherichia coli in hospitals in this area. Methods The genotypes of quinolone-resistant Escherichia coli qnr were determined by PCR amplification and sequencing, preliminary gene location and plasmid conjugation and transfer assay to analyze the characteristics and mechanism of drug resistance. Results Only qnrB gene was positive in each strain of Escherichia coli. The qnrB, qnrS, qnrC, qnrD, qepA and aac (6 ’) - qnrB19 and qnrB31 alleles. Of these qnrB alleles, qnrB31 shares high homology with qnrB16 and qnrB2, and qnrB alleles are located at about 21.0 kb to 28.0 kb long plasmids respectively. Conclusions There are different prevalence of qnrB allele in hospitals in this area. The quinolone resistance of experimental strains is related to the loss of consensus sequence of LexA-protein binding site in the qnrB allele.