title: Mutant selection window and characterization of allelic diversity for ciprofloxacin-resistant mutants of Rhodococcus equi.
abstract: The mutant prevention concentration (MPC) for ciprofloxacin was determined for two Rhodococcus equi strains. The MPC for both strains was 32 mug/ml, which is above the peak serum concentration of ciprofloxacin obtainable by oral administration in humans. Nine single nucleotide changes corresponding to eight amino acid substitutions in the quinolone resistance-determining regions of DNA gyrase subunits A and B were characterized. Only mutants with amino acid changes in Ser-83 of GyrA were highly resistant (>or=64 microg/ml). Our results suggest that ciprofloxacin monotherapy against R. equi infection may result in the emergence of ciprofloxacin-resistant mutants.
authors.affiliation: Microbiology Division, Epizootic Research Center, Equine Research Institute, Japan Racing Association, Shimotsuke, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Niwa
authors.forename: Brent A
authors.initials: BA
authors.lastname: Lasker
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D016929:Rhodococcus equi / Q000145:classification / Q000187:drug effects / Q000235:genetics*; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D059005:Topoisomerase II Inhibitors
chemical_list: D000900:Anti-Bacterial Agents; D059005:Topoisomerase II Inhibitors; D002939:Ciprofloxacin