title: Characterization of fluoroquinolone resistance in Escherichia coli strains from ruminants.
abstract: Thirty-seven fluoroquinolone-resistant Escherichia coli strains from ruminants (according to Clinical and Laboratory Standards Institute guidelines) were screened by molecular methods for mutations in the quinolone resistance-determining region (QRDR) of the gyrA and parC genes and for the presence of the qnrA gene. One of the strains studied was an enterohemorrhagic E. coli (EHEC) strain potentially pathogenic for humans. Three E. coli strains resistant to enrofloxacin (minimal inhibitory concentration [MIC] = 2 microg/ml) but not to ciprofloxacin (MIC = 1 microg/ml) presented single mutations in the gyrA and parC genes, while 34 strains resistant to both fluoroquinolones presented double and single mutations in gyrA and parC, respectively (31 strains), or double mutations in gyrA and parC (3 strains). The EHEC strain presented a double amino acid substitution in the GyrA protein (Ser-83-->Leu and Asp-87-->Gly) and a double amino acid substitution in the ParC protein (Gly-78-->Cys and Ser-80-->Arg), one of which has not been previously described. The present study shows that most of the mutations in the QRDR of the gyrA and parC genes of fluoroquinolone-resistant E. coli strains from ruminants are the same as those seen in E. coli strains from other animal species and humans and that there are no differences in mutation patterns in the QRDR of E. coli strains from healthy ruminants and those with diarrhea. No strains carried qnrA, which indicates that this gene does not play an important role in the selection of fluoroquinolone-resistant E. coli strains from ruminants.
authors.affiliation: Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.
authors.forename: Sonia
authors.initials: S
authors.lastname: Jurado
authors.forename: José A
authors.initials: JA
authors.lastname: Orden
authors.forename: Pilar
authors.initials: P
authors.lastname: Horcajo
authors.forename: Ricardo
authors.initials: R
authors.lastname: De La Fuente
authors.forename: José A
authors.initials: JA
authors.lastname: Ruiz-Santa-Quiteria
authors.forename: Susana
authors.initials: S
authors.lastname: Martínez-Pulgarín
authors.forename: Gustavo
authors.initials: G
authors.lastname: Domínguez-Bernal
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology; D002939:Ciprofloxacin / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D000077422:Enrofloxacin; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D024841:Fluoroquinolones / Q000494:pharmacology*; D012756:Sheep; D012757:Sheep Diseases / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D000077422:Enrofloxacin; D002939:Ciprofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase