Mutations of the gyrA and parC genes of quinolone-resistant bacteria of Shigella spp

Objectives To investigate the quinolone-resistant strains of Shigellaspp.collected in the City of Suzhou in order to provide information for rational selection of antibiotics,to identify mutations of the gyrAand parCgenes in quinolone-resistant Shigellaspp.,and to analyze the relationship between quinolone resistance and amino acid alterations in GyrAand ParC. Methods Seventy-six strains of Shigella bacteria were collected from 3general hospitals in Suzhou,Anhui in China,from 2010to 2012for bacterial identification.A drug susceptibility test was performed using the K-B method and quinolone-resistant gyrAand parCgenes of Shigellalinked to the decision area(QRDR)were detected with apolymerase chain reaction(PCR).The PCR products were subsequently subjected to DNA sequencing. Results Of76strains of Shigella,74(97.4%)were identified as Shigella flexneri and 2(2.6%)were identified as S.sonnei.The susceptibility test indicated that Shigellais highly resistant to amoxicillin,with resistance as high as 100%.Shigellahad the lowest resistance to cefotaxime(6.5%).DNA sequence analysis of genes fromShigellaspp.indicated that quinolone-resistant strains had 3mutations resulting in amino acid changes:Ser83→Leu,Asp87→Gly,and His211→Tyr.Two amino acid residue alterations were observed in the parCgene:Ser80→Ile and Asp197→Asn. Conclusion S.flexneri remains a dominant species in the City of Suzhou.Cefotaxime is the drug of choice for clinical treatment of Shigella-related infection.The resistance of Shigellaspp.to quinolones is related to mutations of the gyrAand parCgenes.The relationship between the amino acid variations GyrA His211→Tyr and ParC Asp197→Asn and quinolone resistance needs to be investigated further.