title: [Fluoroquinolone resistance mutations in topoisomerase genes of Salmonella typhimurium isolates].
abstract: OBJECTIVE
  Mutations in topoisomerase genes were main cause of the resistence of Salmonella typhimurium to fluoroquinolone.
  
  
  METHODS
  The MICs of three Salmonella typhimurium isolates X2, X7, X11 to ciprofloxacin were above 32 microg/ml, 0.38 microg/ml and 0.023 microg/ml, respectively. The genetic alterations in four topoisomerase genes, gyrA, gyrB, parC, and parE were detected by multiplex PCR amplimer conformation analysis in these three strains.
  
  
  RESULTS
  X2 isolate showed both gyrA mutations (Ser83-->Phe, Asp87-->Asn) and parC mutation (Ser80-->Arg). X7 isolate showed a single gyrA mutation (Ser83-->Phe) and X11 isolate had no changes in all of the four quinolone resistance genes, gyrA, gyrB, parC, and parE. X7 isolate with a single gyrA mutation was less resistant to ciprofloxacin than X2 with double gyrA mutations and an additional parC mutation.
  
  
  CONCLUSIONS
  GyrA and parC genes play important role of the resistance of Salmonella typhimurium to ciprofloxacin.
authors.affiliation: Institute of Nutrition and Food Safety, Chinese Center for Disease Prevention and Control, Beijing 100050, China.
authors.forename: Yunchang
authors.initials: Y
authors.lastname: Guo
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Pei
authors.forename: Xiumei
authors.initials: X
authors.lastname: Liu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000187:drug effects / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024841:Fluoroquinolones / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D016133:Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase