Antimicrobial Resistance in Selected Bacteria from Food Animals in New Zealand 2018-2022

Antimicrobial resistance (AMR) presents a significant threat to human health worldwide. One important source of antimicrobial-resistant infections in humans is exposure to animals or animal products. In a phased survey, we investigated AMR in 300 Escherichia coli isolates and 300 enterococci (Enterococcus faecalis and E. faecium) isolates each from the carcasses of poultry, pigs, very young calves, and dairy cattle (food animals); all Salmonella isolates from poultry, very young calves, and dairy cattle; and 300 Campylobacter (Campylobacter jejuni and C. coli) isolates from poultry. The highest resistance levels in E. coli were found for sulfamethoxazole, tetracycline, and streptomycin, for all food animals. Cefotaxime-resistant E. coli were not found and low resistance to ciprofloxacin, colistin, and gentamicin was observed. The majority of enterococci isolates from all food animals were bacitracin-resistant. Erythromycin- and/or tetracycline-resistant enterococci isolates were found in varying proportions from all food animals. Ampicillin- or vancomycin-resistant enterococci isolates were not identified, and ciprofloxacin-resistant E. faecalis were not found. Salmonella isolates were only recovered from very young calves and all eight isolates were susceptible to all tested antimicrobials. Most Campylobacter isolates were susceptible to all tested antimicrobials, although 16.6% of C. jejuni were resistant to quinolones and tetracycline. Results suggest that AMR in E. coli, enterococci, Salmonella, and Campylobacter isolates from food animals in New Zealand is low, and currently, AMR in food animals poses a limited public health risk. Despite the low prevalence of AMR in this survey, ongoing monitoring of antimicrobial susceptibility in bacteria from food animals is recommended, to ensure timely detection of AMR with potential impacts on animal and human health.