发现大肠埃希菌喹诺酮耐药株gyrA基因新亚型和aac(6′)-Ⅰb-Cr、mdfA基因  

Quinolones-resistant gene aac(6′)-Ⅰb-Cr and new subtype gyrA discovered in clinical isolates of Escherichia coli

作　　者：文怡[1] 糜祖煌[2] 刘根焰[1] 顾兵[1] 陈友华[1] 赵旺胜[1] 

机构地区：[1]南京医科大学第一附属医院医学检验科,南京210029 [2]无锡市克隆遗传技术研究所生物信息学室,江苏无锡214026

出　　处：《临床检验杂志》2011年第1期53-54,共2页Chinese Journal of Clinical Laboratory Science

基　　金：江苏省实验诊断学重点实验室重大项目(XK200731)

摘　　要：目的了解大肠埃希菌(E.coli)对常用抗菌药物的耐药性及喹诺酮类DNA旋转酶基因、多药外排基因及氨基糖苷类修饰酶基因(AMEs)的存在情况。方法收集2006年1月～2008年10月本院临床标本分离的E.coli 60株,用K-B法检测细菌对16种抗菌药物的敏感性,用PCR及测序技术分析6种喹诺酮类基因(gyrA、qnrA、qnrB、qnrS、qepA、mdfA)和1种AMEs基因aac(6′)-Ⅰb。结果 60株菌对环丙沙星和左氧氟沙星的耐药率均为78.4%(47/60);55株菌存在gyrA基因突变,其中3株菌gyrA与美国NCB I中已登录的gyrA基因序列不同,为新亚型;mdfA基因均阳性;对9株aac(6′)-Ⅰb基因PCR阳性产物进行测序,证实5株携带aac(6′)-Ⅰb-Cr双功能酶基因。结论 gyrA基因突变是E.coli对喹诺酮类药物最主要的耐药机制,耐喹诺酮类药物的E.coli株中发现aac(6′)-Ⅰb-Cr基因和gyrA新亚型,E.coli检出mdfA基因为中国大陆地区首次报道。Objective To survey the distribution of quinolones-resistant genes,DNA gyrase,multiple-drug efflux pump and aminoglycoside modification enzyme（AME）,in the clinical isolates of Escherichia coli.Methods Sixty strains of E.coli isolated from hospitalized patients were collected from January of 2006 to October of 2008.Susceptibility tests for 16 antibiotics were carried out with disk diffusion method.Six quinolone-resistant genes（gyrA,qnrA,qnrB,qnrS,qepA,mdfA） and a AME [aac（6′）-Ⅰb] were detected by PCR and sequencing.Results Among 60 isolates,resistant rates of ciprofloxacin and levofloxacin were both 78.4%（47/60）.gyrA mutation was found in 55 resistant isolates.All mutated genes were sequenced and blasted with GeneBank of NCBI,and 3 new gyrA mutants were discovered.All resistant strains were mdfA gene-positive and 9 isolates were aac（6′）-Ⅰb-positive by PCR assay in which 5 stains carried bifunction gene aac（6′）-Ⅰb-Cr by sequencing identification.Conclusions Mutation of gyrA gene may be the main mechanism of E.coli.resistant to quinolones.The quinolone-resistant genes aac（6′）-Ⅰb-Cr and new mutants of gyrA were discovered from resistant isolates of E.coli.The resistant gene mdfA of E.coli is firstly reported in Chinese mainland.

关 键 词：大肠埃希菌 喹诺酮 DNA旋转酶 氨基糖苷类修饰酶 基因 

分 类 号：R446.5[医药卫生—诊断学]