季铵盐诱导大肠埃希菌外排泵AcrAB-TolC高表达与氟喹诺酮耐药性关系的研究

Relationship between high expression of efflux pump AcrAB-TolC induced by quaternary ammonium compound and fluoroquinolones resistance in Escherichia coli

目的研究大肠埃希菌AcrAB-TolC外排泵参与季铵盐化合物(quaternary ammonium compound,QAC)与氟喹诺酮类抗生素(fluoroquinolones,FQ)交叉耐药的机制。方法78株大肠埃希菌分离自患者的临床标本,琼脂稀释法检测季胺盐化合物苯扎溴铵的敏感性,随机挑选6株菌,用苯扎溴铵进行诱导,观察菌株诱导前后对苯扎溴铵及环丙沙星敏感性的变化,荧光定量RT-PCR技术检测诱导菌株及其母株外排泵基因acrA、acrB及tolC的mRNA的转录水平。结果78株实验菌株中,苯扎溴铵最低抑菌浓度(minimum inhibitory concentration,MIC)范围为8~64μg/ml,47.4%的菌株MIC值高于标准菌株;诱导株acrA、tolC基因相对表达量明显高于母株,差异有统计学意义;6株诱导株环丙沙星的MIC较母株增加4~8倍。结论推测诱导菌株acrA、tolC基因的转录水平增高与QAC和FQ交叉耐药有一定的相关性。

Objective To investigate the mechanism of efflux pump AcrAB-TolC involved in the cross-resistance between quaternary ammonium compounds(QAC)and fluoroquinolones(FQ)in Escherichia coli.Methods Seventy-eight Escherichia coli strains were isolated from clinical samples and then tested for the sensitivity to benzalkonium bromide by ager dilution method.Six strains were randomly selected and induced with benzalkonium bromide.Changes in the sensitivity of these strains to benzalkonium bromide and ciprofloxacin were analyzed after induction.Expression of the efflux pump genes acrA,acrB and tolC at mRNA level in the induced strains and their parent strains were detected by quantitative real-time PCR.Results Among the 78 strains,the minimum inhibitory concentrations(MIC)ranged from 8μg/ml to 64μg/ml and 47.4%of strains have higher MIC than the standard strain.Compared with the parent strains,the induced strains showed higher expression of acrA and tolC genes,and the differences between the two groups were statistically significant.The MIC values of ciprofloxacin to the six induced strains were 4-8 times higher than those to their parent strains.Conclusions It was speculated that the increased expression of acrA and tolC genes at transcription level in the induced strains were related to the cross-resistance between quaternary ammonium compounds and fluoroquinolone antibiotics.