title: Co-selection may explain high rates of ciprofloxacin non-susceptible Escherichia coli from retail poultry reared without prior fluoroquinolone exposure.
abstract: Australia has never permitted fluoroquinolone use in food-producing animals. We examined local retail poultry for contamination with fluoroquinolone non-susceptible Escherichia coli, then explored the hypothesis that their presence may be due to co-selection of resistance determinants. Between August and November 2010, samples from 30 locally produced, uncooked retail poultry carcasses from four different processing centres underwent selective enrichment culture for ciprofloxacin non-susceptible E. coli. Their chromosomal- and plasmid-mediated resistance determinants were characterized, and phylogenetic analysis and transformation experiments were performed. Unexpectedly, we found nine (30 %) of our small collection of poultry samples carried fluoroquinolone non-susceptible E. coli of which nearly half possessed aac(6')-Ib-cr, a novel plasmid-mediated gene encoding an aminoglycoside acetylating enzyme that also confers fluoroquinolone resistance. All nine isolates were co-resistant to amoxicillin, gentamicin, tetracycline and trimethoprim/sulfamethoxazole--all antibiotic classes that are registered for use in poultry reared for food production within Australia. Their unique phylogenetic relatedness suggested clonal dissemination driven by non-fluoroquinolone selective pressures. aac(6')-Ib-cr was successfully transformed and selected for using non-fluoroquinolone antibiotic pressure. Vertical and perhaps horizontal co-selection may be contributing to the emergence of fluoroquinolone resistance in poultry and could play a similar role in the human setting. This suggests that preservation of the usefulness of fluoroquinolones may require more than just restriction of their use in isolation from other interventions.
authors.affiliation: School of Pathology and Laboratory Medicine, University of Western Australia, Nedlands, WA, Australia.|Department of Microbiology, PathWest Laboratory, QEII Medical Centre, Hospital Avenue, Nedlands, Perth, WA, Australia.
authors.forename: Paul Robert
authors.initials: PR
authors.lastname: Ingram
authors.affiliation: University of Queensland, UQCCR, Brisbane, QLD, Australia.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Rogers
authors.affiliation: University of Queensland, UQCCR, Brisbane, QLD, Australia.
authors.forename: Hanna E
authors.initials: HE
authors.lastname: Sidjabat
authors.affiliation: University of Queensland, School of Veterinary Science, Gatton, QLD, Australia.
authors.forename: Justine S
authors.initials: JS
authors.lastname: Gibson
authors.affiliation: School of Pathology and Laboratory Medicine, University of Western Australia, Nedlands, WA, Australia.|Department of Microbiology, PathWest Laboratory, QEII Medical Centre, Hospital Avenue, Nedlands, Perth, WA, Australia.
authors.forename: Timothy J J
authors.initials: TJJ
authors.lastname: Inglis
mesh_terms: D000123:Acetyltransferases / Q000235:genetics; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001315:Australia; D002876:Chromosomes, Bacterial; D002939:Ciprofloxacin / Q000494:pharmacology*; D016000:Cluster Analysis; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D058889:Molecular Typing; D010802:Phylogeny; D010957:Plasmids; D011200:Poultry / Q000382:microbiology*; D012641:Selection, Genetic; D014169:Transformation, Bacterial
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D000123:Acetyltransferases; C019681:aminoglycoside acetyltransferase