主动外排系统acrAB在志贺菌中分布和表达

目的研究志贺菌患者分离株的多重耐药机制。方法检测志贺菌中有无主动外排系统acrAB-tolC结构基因acrAB-tolC在临床分离菌株中的分布;Northern-blots测定acrAB-tolCmRNA表达水平。结果所有志贺菌分离株染色体中均发现有acrAB-tolC基因,未发现acrAB-tolC基因缺失株;发现4株多重耐药株acrA基因实变,1株敏感野生tolC基因突变,未发现acrB基因突变株。多重耐药株acrA基因mRNA水平显著高于敏感野生株(P<0.05),acrB基因和tolC基因mRNA水平与敏感野生株差异无统计学意义(P>0.05)。结论主动外排系统acrA基因高表达导致临床分离志贺菌产生多重耐药性;acrAB-tolC的表达可能受多种耐药操纵子调控。

Distribution and expression of active efflux pump acrAB in clinical isolates of Shigella

Objective To study the mechanism of multiple-antibiotic-resistance in clinical isolates of Shigella and to detect the distribution and expression of active efflux pump gene acrAB-tolC.Methods Distributions of acrAB-tolC in clinical isolates of Shigella were determined by PCR-SSCP and the levels of acrAB-tolC expression were defermined by Northern-blots.Results acrAB-tolC was found in the all strains;the lack of genes was not foud.The mutation of tolC gene was found in four multiple-antibotic-resistance(Mar)of Shigella and the mutation of tolC gene in one susceptible strains;the mutation of acrB gene was not found.The expression level of acrA gene in the Mar strains was significantly higher than that in the susceptible strains;the mutation of acrB gene was not found.The expression level of acrA gene in the Mar strains was significantly higher than that in the susceptible strains(P>0.05).Conclusion High expression of acrA gene leads to multiple-antbiotic-resistance in clinical isolates of Shigella,and Mar operon may contribute to the regulation of acrAB-tolC gene expression.