临床分离志贺菌属细菌主动外排系统acrAB-tolC基因的表达

目的：探讨临床分离志贺菌属细菌多重耐药机制。方法：从临床收集的141株志贺菌中筛选出64株多重耐药株和6株敏感野生株，应用荧光法测定其对环丙沙星的主动外排功能。PCR—SSCP检测主动外排系统acrAB—tolC基因单链构象多态性。Northern—blot测定acrAB-tolC mRNA表达水平。结果：敏感野生株细胞内环丙沙星稳态浓度高于多重耐药株（P〈0．0001）。所有临床分离志贺菌均检测到acrAB-tolC基因，未发现acrAB-tolC基因缺失株；发现4株多重耐药株acrA基因突变，1株敏感野生株tolC基因突变，未发现acrB基因突变株。多重耐药株acrA基因mRNA表达水平高于敏感野生株（P〈0．05），其acrB基因和tolC基因mRNA表达水平与敏感野生株相比，差异无统计学意义（P〉0．05）。结论：主动外排系统acrA基因高表达可导致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。

Expression of muhidrug active efflux system acrAB-tolC genes in clinical isolated strains of Shigella

Aim: To study the multiple-antibiotic-resistance mechanism in clinical isolated strains of Shigella. Methods: Accumulation of ciprofloxacin in clinical isolates of Shigella was measured by fluorometry. acrAB-tolC genes were detected using PCR-SSCP. The mRNA levels of acrAB-tolC expression were measured using Northern-blot.Results: The concentration of ciprofloxacin in sensitive strains was significantly higher than that in the multiple-antibiotic-resistance (Mar) strains (P<0.000 1). acrAB-tolC was found in all the strains, and the lack of genes was not found. The mutation of acrA gene was found in four Mar strains of Shigella and the mutation of tolC gene, in one susceptible strains, while the mutation of acrB gene was not found. The expression level of acrA gene in the Mar strains was significantly higher than that in sensitive strains (P<0.05), acrB gene and tolC gene had not significant difference(P>0.05). Conclusion: High expression of acrA gene leads to multiple-antibiotic-resistance in clinical isolated strdin of Shigella, and Mar operon may contribute to the regulation of acrAB-tolC gene expression.