Drug resistance mechanism of fluoroquinolone in Shigellae

Objective To investigate the prevalence of quinolone-resistance in Shigella strains,and its relation to the DNA mutations of gyrase and topoisomerase Ⅳ genes.Methods Antimicrobial susceptibility tests were performed in 60 Shigella strains by an agar diffusion method.The quinolone resistance determining region(QRDR) of gyrA,gyrB,parC and parE genes were detected by polymerase chain reaction(PCR) and PCR products of 20 strains were analyzed by nucleotide sequencing.We evaluated the correlation between quinolone resistance and the changes of gyrA,gyrB and parC genes statistically.Results 90.0%,35.0%,28.3% and 15.0 % of tested Shigella strains had NAL,NOR,CIP and LVX drug-resistance,respectively.20 Shigella strains were randomly chosen for gene sequencing and gene mutation rates were 85%(17/20),30%(9/20) and 100%(20/20) for gyrA,gyrB and parC,respectively.There was no mutation confirmed in parE genes.Conclusion The Shigella strains had high frequency of drug resistance to quinolone due to the mutations of gyrA and parC genes.