【摘要】 目的探讨MexAB-OprM、MexXY-OprM主动外排系统(外排泵)在多重耐药铜绿假单胞菌耐药机制中的作用。方法选取25株外科监护室分离的多重耐药铜绿假单胞菌,用实时定量RT- PCR测定结构基因mexA、mexX的mRNA表达水平来判断MexAB-OprM、MexXY-OprM外排泵表达情况；用PCR分别扩增其调控基因mexR、mexZ,并对其产物测序,用Blast软件在GenBank与已知序列比较,研究其过度表达的机理。结果25株多重耐药铜绿假单胞菌中,14株高表达MexAB-OprM系统(56％),3株高表达MexXY-OprM系统(12％),这3株菌同时高表达2种外排泵。在8株mexA高表达的菌株中,5株菌发生mexR基因突变,出现氨基酸替代,1株mexR提前出现终止密码子,2株菌未发现mexR基因突变。2株mexX高表达的菌株均发生基因mexZ突变,出现氨基酸替代。结论主动外排系统MexAB-OprM、MexXY-OprM在多重耐药铜绿假单胞菌中过度表达,是此菌多重耐药机制之一；外排泵MexAB-OprM、MexXY-OprM高表达分别与调控基因mexR、mexZ发生变异有关,同时存在其他调控机制。更多还原

【Abstract】 Objective To investigate the multidrug-resistant mechanisms involved in overexpression of MexAB-OprM,MexXY-OprM active efflux systems in multidrug-resistant Pseudomonas aeruginosa.Methods The expression of the mexA,mexX mRNA was examined by real-time RT-PCR to judge the expression of the MexAB- OprM and MexXY-OprM efflux systems.The controlling gene,mexR and mexZ,whose products downregulate the expression of the MexAB-OprM and MexXY-OprM respectively,were amplified by PCR.Then the amplified prod- ucts were sequenced by automated ABI PRISM 3700.Results Among 25 multidrug-resistant Pseudomonas aerug- inosa,14 strains overexpressed the MexAB-OprM efflux system(56%),3 overexpressed the MexXY-OprM efflux system(12%).Three of them overexpressed both the two efflux systems simultaneously.Among 8 strains overex- pressing MexAB-OprM,5 carried mutations in mesR and had the amino acid substitution in MexR protein,1 had terminal cede at the position of amino acid 32 and 2 had intact mexR gene.All the 2 strains overexpressing MexXY-OprM carried mutations in mexZ and had the amino acid substitution in MexZ protein.Conclusion The overexpression of MexAB-OprM,MexXY-OprM active efflux systems in multidrog-resistant Pseudomonas aerugino- sa,which was caused by the mutations in mexR,mexZ respectively,was one of the multidrug resistance mecha- nisms.Other mechanisms also existed.更多还原