Antibiotic non-susceptible escherichia coli in retail poultry samples from Western Australia

Antibiotic resistance is an emerging threat. Antibiotic use in food producing animals combined with faecal contamination during processing of meat may contribute to transmission of resistant organisms and/or resistance determinants from animals to humans. Previous studies in both Australia and New Zealand have demonstrated low rates of antimicrobial resistant Escherichia coli in retail poultry. None of these studies have detected E.coli resistant to either ciprofloxacin or 3rd generation cephalosporins; both antibiotics recognized as being of critical importance for use in humans. This study aimed to determine the prevalence of antibiotic non-susceptible E.coli in local uncooked poultry using more sensitive methods than in previous studies. Rinses from 30 uncooked chicken carcasses underwent selective enrichment in EC broth then aliquots inoculated onto MacConkey agar plates containing 9 different antibiotics at CLSI susceptibility breakpoint concentrations. The identification and susceptibility of all isolates was confirmed using standard phenotypic methods and disc diffusion according to CLSI criteria. E.coli were isolated from 30/30 (100%) of the poultry samples tested. The proportion of poultry samples from which we were able to detect E.coli that were non-susceptible to antibiotics was: ampicillin (90%), tetracycline (93%), cotrimoxazole (100%), gentamicin (37%), nalidixic acid (63%), ciprofloxacin (30%), ceftazidime (20%), cefotaxime (20%) and chloramphenicol (0%). All isolates demonstrating non-susceptibility to either ceftazidime or cefotaxime carried CMY-2 AmpC beta-lactamase genes. The molecular mechanisms for fluoroquinolone resistance are currently under investigation. The presence of antibiotic non-susceptible E.coli on local, uncooked retail poultry was more frequent than previously demonstrated. Rates of resistance were higher in classes of antibiotics used by the Australian food producing industry. Our finding of resistance to fluoroquinolones and 3rd generation cephalosporins (neither of which are licensed for use in rearing poultry for food producing purposes) warrants further investigation.