title: Fluoroquinolone-resistant Brucella melitensis mutants obtained in vitro.
abstract: Three fluoroquinolone-resistant Brucella melitensis mutants were obtained after successive passages on norfloxacin-containing agar plates. The original strain was B. melitensis biovar 2 ATCC 23457. Mutants emerged at frequencies ranging between 1 x 10(-6) and 3 x 10(-8). The three mutants showed a gyrA Ala71-->Ser mutation as well as insertion of Ala340. No mutations were observed in the parC and gyrB genes. Minimum inhibitory concentrations (MICs) increased by four- to eight-fold from the wild-type to the first-step mutant for norfloxacin, ciprofloxacin, levofloxacin and moxifloxacin. MICs of the second-step mutant increased significantly only for norfloxacin and those for the third-step mutant for norfloxacin and ciprofloxacin, suggesting the involvement of some efflux mechanism.
authors.affiliation: Departamento de Microbiología, Hospital Universitario de Salamanca, Paseo de San Vicente 58-182, 37007 Salamanca, Spain.
authors.forename: Francisco García
authors.initials: FG
authors.lastname: Lázaro
authors.forename: R Elisa
authors.initials: RE
authors.lastname: Rodríguez-Tarazona
authors.forename: José Angel
authors.initials: JA
authors.lastname: García-Rodríguez
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Muñoz-Bellido
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001372:Aza Compounds / Q000494:pharmacology; D017347:Brucella melitensis / Q000187:drug effects / Q000235:genetics; D002939:Ciprofloxacin / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis / Q000187:drug effects / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024841:Fluoroquinolones / Q000494:pharmacology*; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D009154:Mutation; D009643:Norfloxacin / Q000494:pharmacology; D015242:Ofloxacin / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D001372:Aza Compounds; D004269:DNA, Bacterial; D024841:Fluoroquinolones; D011804:Quinolines; D002939:Ciprofloxacin; D064704:Levofloxacin; D015242:Ofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase; D009643:Norfloxacin; D000077266:Moxifloxacin