氟喹诺酮类药物体外诱导大肠埃希菌耐药性观察

Observation of Escherichia coli induced resistance to fluoroquinolones in vitro

目的:探讨大肠埃希菌在氟喹诺酮类最低抑菌浓度(MIC)下耐药性的产生,以指导临床合理使用抗生素。方法:采用多步诱导法,对32株临床分离的氟喹诺酮类敏感大肠埃希菌分别进行环丙沙星、左氧氟沙星和加替沙星的诱导性耐药试验;用琼脂稀释法测定诱导前后敏感菌株的药物敏感性;用PCR方法测定耐药基因序列。结果:22株大肠埃希菌诱导出稳定的高耐氟喹诺酮菌株;与原株比较,耐药株的MIC分别增加了32～3000倍;进行测序的6株诱导耐药菌株均发生gyrA的83Ser→Leu、87Asp→Asn和parC的80Ser→Ile突变,而测序的1株敏感菌株未发现基因突变。结论:在低浓度抗菌药物的长期压力下,可诱导大肠埃希菌产生对氟喹诺酮类的获得性耐药。

Aim：To observe the induced resistance of Escherichia coli to a variety of fluoroquinolones in drug concentration of sub-MIC.Methods：The experiments on induced resistance to ciprofloxacin,levofloxacin or gatifloxacin were performed,in thrity-two Escherichia coli sensitived to fluoroquinolones from clinic,respectively,by multiple-step method.The susceptibility of the induced strains resistant to fluoroquinolones was measured by determining the MIC using agar dilution method.Results：The strains highly resistant to fluoroquinolone were obtained from 22 tested strain of Escherichia coli,the MICs of these laboratory resistant strains were with 32 to 3 000 fold increase,respectively,when compared with parent strains.All six induced highly resistant strains examined carried two gyrA mutations affecting residues 83Ser→Leu,Asp87→Asn and one parC mutation of 80Ser→Ile.No mutation was found in a susceptible isolate.Conclusion：Acquired resistance could be occurred when exposing to low level of some fluoroquinolones for long term.