耐喹诺酮类药物沙门菌毒力岛基因和耐药基因突变研究

Mutations of Salmonella pathogenicity island gene and QRDRs genes in quinolone-resistant Salmonella strains

目的:研究耐喹诺酮类药物沙门菌毒力岛基因和喹诺酮耐药基因在不同血清型及耐环丙沙星菌株中基因变异情况。方法:对分属于6个不同血清型的40株沙门菌测定环丙沙星MIC;对沙门菌毒力岛Ⅰ的3个主要基因和喹诺酮耐药基因进行测序比对,分析其基因变异情况及与毒力的关系。结果:40株沙门菌其毒力岛Ⅰ的3个基因全部为阳性,不同血清型其基因序列存在不同程度的变异;环丙沙星耐药株喹诺酮耐药基因gyrA均发生了S83F和/或D87N/G点突变,parC基因发生了S87R的点突变。结论:毒力岛Ⅰ基因在不同血清型的变异,说明其毒力仍在进化中;环丙沙星并未引起沙门菌毒力岛基因突变或缺失,但喹诺酮耐药基因均发生了点突变,这可能与其毒力降低相关。

Objective： To study the gene variations of Salmonella pathogenicity island - 1 （ SPI - 1 ） genes and quinotone resistance -determining regions （QRDRs） genes in different serovars and ciprofloxacin -resistant SalomoneUa strains. Methods： The minimal inhibitory concentrations （MICs）for ciprofloxacin were determined u- sing the standard broth microdilution method on 40 Salmonella strains in 6 serovars. Three SPI - 1 genes and QRDRs genes were sequenced and compared in different Salmonella strains to analyze the gene mutations and the re- lationship with Salmonella virulence. Results： Three SPI - 1 genes were detected in all the 40 Salmonella strains, but the base variations belonging to silent mutations were observed in different serovars. No gene deletion or mutation was observed in SPI - 1 genes, but gyrA point mutations （$83F and/or D87N/G） and parC point mutation （S87R） were observed in all the 40 ciprofloxacin - resistant strains. Conclusion： The SPI - 1 gene variations showed the e- volution of virulence in Salmonella. Ciprofloxacin may not induce gene sequence variation or deletion of SPI - 1 genes. However, the gyrA gene mutations may indicate the virulence reduction of Salmonella strains.