大肠埃希菌对氟喹诺酮类的质粒介导耐药机制研究

Plasmid-mediated fluquinolne resistance in Escherichia coli

目的了解近年来发现的质粒介导耐药机制在临床分离大肠埃希菌中对氟喹诺酮类耐药所起的作用。方法用MIC琼脂稀释法筛选耐左氧氟沙星大肠埃希菌;采用聚合酶链反应对qnrA、qnrS、qnrB、aac(6′)-Ib基因进行扩增,并进行PCR扩增产物直接双向测序。用接合实验了解是否存在水平传播的氟喹诺酮耐药性传播机制。结果 90株耐氟喹诺酮类大肠埃希菌中7株检出aac(6′)-Ib-cr基因,未检出qnrA、qnrS、qnrB基因。78株符合供体菌标准的大肠埃希菌中有2株接合成功,接合率2.6%。结论该地区存在质粒介导的氟喹诺酮类耐药性的水平传播。

Objective To investigate the importance of recently discovered plasmid-mediated resistance in the development of fluquinolone resistance in clinical isolates of Escherichia coil（E, colD. Methods Strains of E. coli resistant to levofloxacin were selected by Kirby-Bauer disk diffusion method, and the qnra, qnrS, qnrB and aac （61）-Ib genes were amplified by polymerase chain re- action（PCR） and sequenced by forward and reverse sequencing. Conjugation test was used to determine the plasmid-mediated flu- quinolone-resistance. Results The aac（61）-Ib-cr gene were detected in 7 of 90 isolates of E. coli and the qnrA,qnrS and qnrB genes were not found. In 78 strains of E. eoli, coincident with the criterion of donor bacterial, 2 strains were found with transconjugants and the conjugation rate was 2.6%. Conclusion There should be plasmid-mediated fluquinolone-resistance genes in the isolates of E coli and the horizontally transferable elements of fluquinolones-resistance in this hospital.