title: Fluoroquinolone resistance in Mycoplasma gallisepticum: DNA gyrase as primary target of enrofloxacin and impact of mutations in topoisomerases on resistance level.
abstract: Resistant mutants of Mycoplasma gallisepticum were selected in vitro by passaging strains 10 times in increasing concentrations of enrofloxacin. The regions of gyrA/gyrB and parC/parE, encoding the quinolone resistance-determining regions (QRDRs) of DNA gyrase and DNA topoisomerase IV, respectively, of the mutants obtained during different passages were sequenced. Several mutations were found in the four fluoroquinolone targets. Substitution of Ser-83-->Arg in GyrA and Ser-80-->Leu or Trp in ParC QRDRs seem to have the greatest impact on resistance to fluoroquinolones. The results obtained also suggest that the preferential target of enrofloxacin in M. gallisepticum is DNA gyrase.
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D027081:DNA Gyrase / Q000378:metabolism*; D026942:DNA Topoisomerases / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D000077422:Enrofloxacin; D024841:Fluoroquinolones; D009154:Mutation / Q000235:genetics*; D009174:Mycoplasma / Q000187:drug effects* / Q000235:genetics; D015363:Quinolones / Q000494:pharmacology*
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D015363:Quinolones; D000077422:Enrofloxacin; D026942:DNA Topoisomerases; D027081:DNA Gyrase