大肠埃希菌对喹诺酮类抗菌药物耐药机制研究

Study on drug resistant mechanisms of Escherichia coli to quinolone

目的了解大肠埃希菌(ECO)对喹诺酮类抗菌药物耐药机制,为临床合理使用抗菌药物提供参考依椐。方法选取2011年2-6月连云港地区医院临床分离的ECO 62株,采用PCR扩增ECO的gyrA和parC基因,并作序列分析,检测喹诺酮类抗菌药物作用靶位(拓扑异构酶)突变;PCR法检测qnrA、qnrB、qnrS和aac(6′)-Ibcr 4种质粒介导耐药基因,观察分析各种耐药机制对喹诺酮类抗菌药物MIC值及敏感性影响,数据采用SPSS17.0软件进行统计分析。结果 62株ECO中有36株发生gyrA基因变异,parC基因突变共42株,所有gyrA基因的变异均同时发生parC基因突变;10株菌检测质粒介导的耐药基因扩增阳性,其中qnrB基因1株、qnrS基因4株、aac(6′)Ib-cr基因5株,未检测到qnrA基因;共有2株菌检测到膜泵外排机制;所有喹诺酮类耐药菌株均存gyrA基因突变,其他耐药机制虽然使萘啶酸和环丙沙星的MIC有不同程度升高,但均在敏感范围以内。结论 ECO对喹诺酮类抗菌药物存在多种耐药机制,靶位(拓扑异构酶)突变是引起ECO对喹诺酮类抗菌药物耐药的主要原因。

OBJECTIVE To investigate the drug resistant mechanism of Escherichia coli （E .coli） to quinolone so as to provide a scientific basis for rational use of antimicrobial drugs in clinical treatment .METHODS A total of 62 non‐repetitive E .coli clinical isolates were collected from three hospitals in Lianyungang area from Feb .to Jun . 2011 .GyrA and parC genes were amplified by PCR and the Quinolone target position （topoisomerase） mutations were detected by sequence analysis .Four plasmid‐mediated resistance genes （qnrA ,qnrB ,qnrS and aac （6′）‐Ib‐cr） were detected by PCR .The impaction of various resistance mechanisms on quinolone MIC and sensitivity in E . coli was observed .All data were statistically analyzed by SPSS 17 .0 software .RESULTS Target （topoisomerase） mutations were identified in 42（67 .7% ） strains out of 62 strains .Among them ,gyrA mutations were detected in 36 strains and parC mutations were identified in 42 strains which occurred simultaneously along with gyrA muta‐tion .Plasmid‐mediated resistant gene were expressed in 10 strains ,including qnrB positive （1 strain） ,qnrS posi‐tive （4 strains） and aac （6′） Ib‐cr positive （5 strains） .However ,qnrA gene was not detected ;membrane efflux pump mechanisms were detected in 2 strains .The result showed that gyrA mutations existed in all the quinolone resistant strains ,although other resistance mechanisms had increased NAL and CIP MIC which were within the sensitive range .CONCLUSION M ultiple mechanisms are involed in E .coli to quinolone in Lianyungang and target （topoisomerase） mutations play an important role in quinolone resistant in E .coli .