目的 明确产超广谱β-内酰胺酶(esbls)菌株对喹诺酮类药物的耐药机制.方法 用pcr方法扩增产esbls的263株大肠埃希菌和99株肺炎克雷伯菌的qnra基因.对ctx-m和qnra基因都阳性的肺炎克雷伯菌zj96采用接合试验、southern杂交进行基因定位,用鸟枪法对分离自zj96菌株的同时含qnra和ctx-m基因的质粒(pkp96)进行全序列测定.结果 263株大肠埃希菌中有5株检出qnra基因,阳性率为1.9%;99株肺炎克雷伯菌中有8株检出qnra基因,阳性率为8.1%.zj96菌株含有ctx-m和qnra基因同时阳性的大小约60 kb的接合性质粒pkp96.菌株zj96的接合菌质粒pkp96含有qnra、ctx-m-24、aac(6')-ib-cr、teta和intⅠ 1等基因.结论 喹诺酮耐药基因qnra和ctx-m-24型esbls基因同时位于可接合性质粒中,耐药质粒的广泛传播是造成临床耐药菌株大量出现的主要原因.
abstract：
objective to characterize the prevalence of plasmid-mediated quinolone resistance determinants qnra in extended-spectrum β-lactamase(esbl)-producing escherichia coli and klebsiella pneumonia.methods pcr was used to amplify qnra gene in esbl-rpoducing isolates(including 263isolates of escherichia coli and 99 isolates of klebsiella pneumonia).conjugation experiments and southern blot hybridization were employed to definitude the location of the genes in zj96 isolate of klebsiella pneumonia which had positive qnra and ctx-m genes.shot gun sequencing was performed for analyzing the complete nucleotide sequence of pkp96,a plasmid containing qnra and ctx-m-24 genes in zj96 isolate.results qnra was detected in 5 out of 263(1.9%)escherichia coli isolates and 8 out of 99(8.1%)klebsiella pneumonia isolates.pkp96,a conjugative plasmid including qnra gene and ctx-m-24 gene presented in zj96 isolate.the sequence of the plasmid pkp96 displayed the qnra,ctx-m-24,aac(6')-ib-cr,teta and int Ⅰ 1 genes.conclusion the plasmid-mediated genes,such as qnra and ctx-m,may facilitate the prevalence of multi-drug resistant strains.
