Evaluating antimicrobial resistance in Campylobacter coli and Campylobacter jejuni isolated from market hogs and sows at U.S. slaughter plants (2013–2021): A longitudinal comparative analysis

The emergence of antimicrobial resistance (AMR) in Campylobacter spp. isolates pose a food safety risk. Data on AMR in Campylobacter spp . isolated from swine at U.S. slaughterhouses between 2013 and 2021, collected by the National Antimicrobial Resistance Monitoring System (NARMS), were analyzed. A total of 2659 isolates, 1694 from market hogs (1599 C. coli and 95 C. jejuni ) and 965 from sows (918 C. coli and 47 C. jejuni ) were included. C. coli isolates had a higher resistance to all tested antimicrobials. All Campylobacter species isolated from market hogs showed a higher resistance. A high resistance to tetracycline was observed in C. coli isolates of both swine sources (75–83 %). Moderate to high resistance was identified to macrolides (azithromycin, erythromycin: 15–29 %) and lincosamides (clindamycin: 21–41 %), while quinolone resistance (ciprofloxacin, nalidixic acid: 10–19 %) was moderate. After adjusting for Campylobacter species and production type, compared to the reference year 2013, the odds of resistance to nalidixic acid (ORs: 2.00–5.40) and ciprofloxacin (ORs: 1.05–3.17) were significantly increasing throughout the study period (2014–2021). For macrolides, compared to the reference year 2013, the odds of resistance were significantly decreasing (azithromycin (ORs: 0.69–0.60), and erythromycin (ORs: 0.69–0.58)) in the later years of the study period (2019–2021). The co-resistance network revealed interconnected resistance patterns in C. coli isolates from market hogs, suggesting that they may serve as an AMR reservoir. Swine production type-specific interventions are needed to reduce AMR in Campylobacter spp. across the food production chain. • High tetracycline resistance was observed in C. coli in both swine sources. • C.jejuni and C. coli from market hogs showed higher resistance than sow isolates. • C. coli isolates from market hogs had broader co-resistance networks than C. jejuni isolates. • An increasing odds of quinolone resistance and decreasing odds of macrolide resistance were observed.