80株大肠埃希菌靶位基因突变对喹诺酮耐药影响  

Effects of target gene mutations on the quinolones resistance in 80 clinical isolates of Escherichia coli

作　　者：赵瑞华[1] 舒明星[1] 陈淑贞[1] 

机构地区：[1]中南大学湘雅医学院微生物学教研室,湖南长沙410078

出　　处：《中国感染控制杂志》2002年第1期12-15,共4页Chinese Journal of Infection Control

摘　　要：目的　探讨大肠埃希菌靶位基因突变对喹诺酮类药物耐药的影响。方法　本研究分别用琼脂稀释法和K -B纸片扩散法药敏试验检测了 80株致泌尿系感染的大肠埃希菌环丙沙星MIC的分布和对四种喹诺酮类药物的敏感性 ;PCR扩增大肠埃希菌的gyrA和 parC基因的QRDR区 ,分别对其进行限制性内切酶酶切分析和SSCP分析 ,以检测药物靶位基因可能存在的突变。结果　 80株致泌尿系感染的大肠埃希菌中有 4 7株对环丙沙星耐药 ,耐药率达 5 8.75 % ,2 0株对环丙沙星敏感的菌株 gyrA基因QRDR区未发生改变 ,而 13株敏感株和 4 7株耐药株gyrA 2 4 7bp位点处均存在突变 ,且这 13株对环丙沙星敏感的菌株均对萘啶酸耐药。 33株对环丙沙星敏感的菌株parCSSCP分析 ,均未存在突变。 结论　① 80株致泌尿系感染的大肠埃希菌对环丙沙星的敏感性和对萘啶酸的敏感性存在明显差异 ;②gyrA基因是大肠埃希菌喹诺酮类药物的主要作用靶位。在某些菌株中 ,其 2 4 7位核苷酸位点的改变仅使细菌对环丙沙星的敏感性下降 ,parCQRDR区的突变使细菌的耐药程度增加。Objective To investigate the effects of target gene mutations on the quinolones resistance in Escherichia coli. Methods The study detected the distribution of ciprofloxacin MICs and the susceptibility to four quinolones in 80 clinical isolates of Escherichia coli which resulted in urinary tract infections by agar dilution test and K B disk diffusion method respectively. In order to investigate the mutations in the target genes, the fragments of QRDR of gyrA and parC were amplified and these fragments were analyzed by restriction fragment length polymorphism and single strand conformation polymorphism analysis. Results Forty seven of 80 clinical isolates of Escherichia coli which led to the UTI were resistant to ciprofloxacin. The mutation of 247 bp was not found in 20 susceptible strains to ciprofloxacin, but it existed in 13 susceptible strains and 47 isolates resistant to ciprofloxacin, and the 13 susceptible isolates to ciprofloxacin were resistant to nalidixic acid. The parC QRDR mutation was not found in these 33 susceptible strains. Conclusions ① There is obvious difference in susceptibility to ciprofloxacin and to nalidixic acid in 80 clinical isolates of Escherichia coli which lead to the UTI; ② DNA gyrase is the primary target of quinolones, but in some strains, the single site change of nucleotide 247 only leads to the reduced susceptibility to ciprofloxacin, and the simultaneous presence of the parC QRDR alternations can increase the level to quinolone resistance.

关 键 词：大肠埃希菌 喹诺酮类药物 靶位基因 GYRA PARC 

分 类 号：R378.2+1[医药卫生—病原生物学]