临床分离的美罗培南和环丙沙星共同耐药的铜绿假单胞菌耐药机制的研究

摘要

目的：探讨临床分离的对美罗培南和环丙沙星均耐药的铜绿假单胞菌的耐药机制。方法收集经VITEK-2 Compact微生物分析系统检测为美罗培南和环丙沙星耐药的铜绿假单胞菌30株，琼脂稀释法复查最小抑菌浓度（MIC）值。改良三维试验检测碳青霉烯酶，聚合酶链反应（PCR）扩增耐药基因，逆转录PCR 分析细菌外排系统表达情况。结果琼脂稀释法与VITEK-2 Compact微生物分析系统检测结果相同。所有菌株均未产碳青霉烯酶，PCR扩增测序未发现基因改变，逆转录PCR检测外排系统发现以mexX和mexC基因表达增加为主，其调控基因扩增测序发现4株mexC过度表达的调控基因nfxB Gly→Val（GGC→GTC），6株mexX过度表达的调控基因mexZ Val→Gly（CTG→CAG）。结论外排系统调控基因突变而引起的外排系统MexXY-OprM和MexCD-OprJ过度表达是引起美罗培南和环丙沙星耐药的主要原因。%Objective To investigate the drug resistance mechanisms of both meropenem and ciprofloxacin in clinical isolates of Pseudomonas aeruginosa.Methods A total of 30 isolates of Pseudomonas aeruginosa which had been tested resistance to both meropenem and ciprofloxacin by VITEK-2 Compact were collected.Agar dilution method was used to reexamine the minimal inhibitory concentrations (MIC)of meropenem and ciprofloxacin.Carbapenemases were detected by modified three-dimensional test.The resistance genes were analyzed by polymerase chain reaction (PCR) amplification.The expression of efflux systems was analyzed by reverse transcription PCR.Results The same results were showed between agar dilution method and VITEK-2 Compact.Carbapenemases were not detected by modified three-dimensional test.The overexpression of mexX and mexC genes were detected by reverse transcription PCR.The sequencing of regulatory genes showed that there were 4 isolates which the Gly(GGC)of nfxB was substitute for Val (GTC)and 6 isolates which the Val(CTG)of mexZ was substitute for Gly (CAG).Conclusions The overexpression of the MexXY-OprM and MexCD-OprJ efflux system,due to the mutation of regulatory genes of efflux system,is contributed to the drug resistance to both meropenem and ciprofloxacin of Pseudomonas aeruginosa.