耐左氧氟沙星大肠埃希菌gyrA/gyrB/parC/parE基因突变研究

目的了解耐氟喹诺酮大肠埃希菌gyrA／gyrB／parC／parE基因突变情况。方法用Kirby—Bauer琼脂扩散法筛选耐左氧氟沙星大肠埃希菌；采用聚合酶链反应（PCR）对gyrA／gyrB／parC／parE基因进行扩增，并进行PCR扩增产物直接双向测序，分析上述基因突变情况。结果PCR扩增耐菌株gyrA／gyrB／parC／parE基因，获得目的片段，测序结果显示，氟喹诺酮耐药基因突变集中在gyrA基因83、87位ser→Leu、Asp→Asn突变；parC基因55位Ser→Leu突变，部分菌株尚存在62位Gln→Glu第二突变点；未发现gyrB、parE突变。结论靶位点gyrA和parC的改变，是本地大肠埃希菌对氟喹诺酮类耐药的主要机制。

The study on the mutations in gyrA/gyrB/parC/parE genes for levofloxacin-resistant Escherichia coli

Objective To investigate the mutations in gyrA/gyrB/parC/pareE genes for fluquin-olone-resistanct Escherichia coil. Methods Levofloxacin-resistant Escherichia coli strains were screened by Kirby-Bauer disk diffusion method and gyrA/gyrB/parC/parE genes were detected by applying polymerase chain reaction (PCR). The point mutations were found by direct two-way sequencing of the PCR products. Results The gyrA/gyrB/parC/parE genes of levofloxacin-resistant resistant Escherichia coli stains were amplified by PCR mehtod. The point mutations of the gyrA/parC genes were found, which were gyrA 83 Ser→Leu, 87 Asp→Asn and parC 55 Ser→Leu, 62 Gln→Glu. No mutations of gryB and parE genes were found. Conclusion Mutations in gyrA and parC are the most important mechanism of fluoroquinolone resistance to Escherichia coli in our area.