铜绿假单胞菌对喹诺酮类药物的耐药机制研究

The mechanism of quinolone resistance in Pseudomonas aeruginosa

目的研究临床分离的铜绿假单胞菌对喹诺酮类药物的耐药机制。方法用琼脂稀释法测定临床分离的铜绿假单胞菌对环丙沙星和左氧氟沙星的最小抑菌浓度（MIC）以及加入羰基氰氯苯腙（CCCP）后的MIC；用PCR扩增gyrA及parC基因的喹诺酮耐药决定区，并对扩增产物进行测序分析；用肠杆菌基因间重复序列PCR（ERIC—PCR）对铜绿假单胞菌进行基因分型。结果20株临床分离株中，16株对喹诺酮类药物耐药，4株敏感；CCCP未能显著降低耐药株对环丙沙星和左氧氟沙星的MIC；16株耐菌株在gyrA均有Thr-83→Ile的改变，在parC均有Ser-87→Leu的改变；ERIC—PCR显示这16株耐药株电泳图谱一致，属于同一基因型，与敏感株有明显区别。结论gyrA合并parC基因突变是临床分离的铜绿假单胞菌对喹诺酮类药物耐药的主要机制。

Objective To investigate the mechanism of quinolone resistance in Pseudomonas aeruginosa. Methods The minimum inhibitory concentrations （MICs） of eiprofloxaein and levofloxaein with and without carbonylcyainde-m-chlorophenylhydrazone （CCCP） were determined by agar dilution method. Polymerase chain reaction （ PCR ） and DNA sequencing were used to study the mutations in quinolone resistance-determining region of gyrA and parC genes. The strains were genotyped by enterbaeterial repetitive intergenic consensus-PCR （ERIC-PCR）. Results Sixteen quinolones-resistant Pseudomonas aeruginosa strains were obtained. The MICs of ciprofloxacin and levofloxacin were not reduced significantly by adding CCCP. Thr - 83→Ile of gyrA and Ser - 87→Leu ofparC were found simultaneously in 16 strains of resistant Pseudomonas aeruginosa. Analysis of ERIC-PCR products indicated that 16 quinolone-resistant strains had an identical band pattern which was different from that seen in the sensitive strains. Condusion Mutations in gyrA and parC may be the main mechanism of quinolone resistance in clinical isolates of Pseudomonas aeruginosa.