212～216年广东省中山社区鼠伤寒沙门菌同源性分析及对喹诺酮类药物耐药机制研究

目的 研究广东省中山社区鼠伤寒沙门菌(STM)的同源性及对喹诺酮类药物的耐药机制。方法 收集中山大学附属中山医院2012年3月～2016年12月临床分离鼠伤寒沙门菌78株(排除同一病人重复送检菌株)。通过琼脂稀释法检测鼠伤寒沙门菌对喹诺酮类药物的敏感度; 脉冲电场凝胶电泳(PFGE)方法分析耐药菌株的同源性; 使用PCR和DNA测序法分析gyrA,gyrB,parC和parE基因喹诺酮耐药决定区(QRDRs)的突变; PCR检测质粒介导喹诺酮类药物耐药基因qnr(qnrA,qnrB,qnrS,qnrD)和aac(6')-Ib-cr。结果 33株鼠伤寒沙门菌对环丙沙星产生耐药。33株鼠伤寒沙门菌共产生33种不同的PFGE图谱,相似度小于90%。29株耐药株gyrA位点发生单突变导致在第83或87位存在唯一氨基酸替代,其中第83位突变率占93.1%(27/29)。4株喹诺酮高耐药菌株的gyrA同时存在83和87号位双突变导致两个氨基酸发生替代,其中2株菌额外出现parC基因单碱基突变导致第80号位出现氨基酸替代。所有菌株中均未检测到qnr基因,但有15株鼠伤寒沙门菌检出aac-(6')-Ib-cr基因。结论 中山社区鼠伤寒沙门菌对喹诺酮类药物耐药性较高,主要机制是gyrA基因的单突变和携带aac-(6')-Ib-cr耐药基因。

Study on the Homology and Resistance Mechanism of Salmonella Typhimurium to Quinolone from 2012 to 2016 in Zhongshan Community of Guangdong Province

Abstract:Objective Study on the homology and mechanism of quinolones-resistance in Salmonella typhimurium(STM)in Zhongshan community of Guangdong Province.Methods 78 strains of Salmonella typhimurium(the same strains from the same patient were excluded)were isolated from March 2012 to December 2016 in Affiliated Sun Yat-sen Hospital of SunYat-sen University.Antibiotic susceptibility testing for these isolates wereperformed by the agar dilution method.The PFGE was used to determine the existence of the same clone strains in Salmonella typhimurium strains.PCR and DNAsequencing were used to investigate the mutation in the quinolone resistance-determining regions(QRDRs)(include gyrA,gyrB,parC and parE)and detected theplasmid-mediated quinolones-resistance genes qnr(qnrA,qnrB,qnrS,qnrD)andaac(6')-Ib-cr.Results Totally 33(42.3%)of 78 Salmonella typhimurium isolates were resistant to ciprofloxacin.33 different PFGE patterns were appeared among the selected strains with the genetic similarity under 90%.29 isolates had a single mutants in the ORDRs of gyrA,and 93.1%(27/29)of these isolates had the position No.83 mutations.The double mutant in the QRDRs of gyrA were detected in both of four ciprfloxacin-resistant Salmonella typhimurium,with the additional one mutation in parC in two of them carried the mutant in position No.80.Qnr was not detected in all of the isolates,but aac-(6')-Ib-cr gene was detected in 15(19.2%)isolates.Conclusion There was high quinolones-resistance in Salmonella typhimurium in Zhongshan Community infections.The single mutation in the QRDRs of gyrAand its containing aaac-(6')-Ib-cr were the key mechanism for the resistances.