Analyses on genetic mutations in quinolone-resistant Shigellae flexneri

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 .