Co-selection may explain high rates of ciprofloxacin non-susceptible Escherichia coli from retail poultry reared without prior fluoroquinolone exposure

Paul Robert Ingram, Benjamin A. Rogers, Hanna E. Sidjabat, Justine S. Gibson, Timothy J.J. Inglis

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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.

Original languageEnglish
Pages (from-to)1743-1746
Number of pages4
JournalJournal of Medical Microbiology
Issue numberPART 11
Publication statusPublished - Nov 2013
Externally publishedYes

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