耐喹诺酮类福氏志贺菌基因突变分析

Analyses on genetic mutations in quinolone-resistant Shigellae flexneri

目的 研究福氏志贺菌DNA旋转酶gyrA基因、拓扑异构酶ⅣparC基因突变与其喹诺酮类药物耐药的关系。方法 对临床收集的 1株喹诺酮类药物敏感福氏志贺菌、2株喹诺酮类药物耐药程度不同的福氏志贺菌 ,对上述2个靶基因进行聚合酶链反应 (PCR)扩增及核酸序列分析。结果 首次发现临床分离喹诺酮类耐药福氏志贺菌parC基因突变 ,导致 12 1,12 9,131,134,14 1,15 1位 5个位点氨基酸编码改变 ;耐药程度较高的菌株共发现gyrA、parC基因上 6个突变位点 ,耐药程度较低的菌株发现gyrA基因 1个突变位点。结论 福氏志贺菌DNA旋转酶gyrA基因和拓扑异构酶ⅣparC基因突变均与其喹诺酮类药物耐药有关 ,靶基因突变位点数量可能与喹诺酮类药物耐药程度有关 ,临床耐药株靶基因突变存在多态性。

Objective To study the correlation of quinolone resistance with mutations in DNA gyrase gyrA gene and topoisomerase ⅣparC gene in clinical isolates of Shigellae flexneri .Methods The N-terminal coding region of gyrA and parC genes were amplified by polymerase chain reaction(PCR) repectively and sequenced in two quinolone-resistant clinical isolates with different resistant level and one quinolone-sensitive clinical isolate.Results DNA sequence analysis of parC in clinical isolate of quinolone-resistance Shigellae flexneri firstly revealed five point mutations that resulted in amino acid change:129-Ser→Ala,131-Leu→Val,134-Ser→Gly,141-Ala→Val,151-Leu→Met.One isolate with higher resistance was found carrying six point mutations in gyrA and parC.The other one with lower resistance was found carrying one point mutation in gyrA.No mutation was found in gyrA or parC in clinical isolate of quinolone-sensitive Shigellae flexneri .Conclusion The mutations of gyrA gene and parC gene were implicated in the resistance of Shigellae flexneri to quinolone.The total number of mutations were related to the level of resistance to quinolones.There was heterogeneity of mutations in the clinical isolates of quinolone-resistant Shigellae flexneri .