Purpose: In this study, the efficacy of antibiotic-free (ABF) management practices was assessed by monitoring the prevalence of AMR Campylobacter in a commercial broiler processing plant.
Methods: Fecal grab samples, carcass rinses, water samples, equipment swabs, and air samples were collected from a commercial processing plant on 16 different days within a 12-month time frame. Campylobacter was isolated by direct plating on Campy-Cefex agar along with simultaneous enrichment in Bolton’s broth. Two isolates were collected per positive sample and confirmed by PCR. These isolates were then tested for antimicrobial resistance using commercially prepared broth micro-dilution plates and the National Antimicrobial Resistance Monitoring System (NARMS) protocol.
Results: A total of 312 PCR-confirmed Campylobacter isolates were tested for AMR and 7.1% (22 isolates) were resistant to 3 or more antimicrobials. The most common resistance observed was against tetracycline, with a prevalence of 72.8% (227 isolates). This was followed by nalidixic acid resistance at 7.4% (23 isolates), clindamycin resistance at 6.7% (21 isolates), and ciprofloxacin resistance at 6.1% (19 isolates). Resistance to all other antimicrobials tested was under 3.0%, including erythromycin (2.2%).
Significance: These results demonstrate that AMR Campylobacter remains present even in plants that process ABF chicken. Of particular concern was the detection of isolates resistant to important drugs for treating severe campylobacteriosis such as erythromycin (7 isolates) and ciprofloxacin (21 isolates). These findings reinforce the importance of interventions to control overall pathogen prevalence and highlight the continuing need for research on management strategies for AR pathogens.