Modeling multidrug resistance in Campylobacter coli and Campylobacter jejuni isolated from swine at U.S. slaughter plants.

Antimicrobial-resistant and multidrug-resistant Campylobacter spp. poses a human health risk. A total of 1694 isolates from market hogs (1599 Campylobacter coli and 95 C. jejuni) and 965 isolates from sows (918 C. coli and 47 C. jejuni) that were isolated at US slaughter plants from 2013 to 2021 and tested for antimicrobial resistance were included in the analysis. Multidrug resistance (MDR) (resistance ≥ antimicrobial classes) was highest in C. coli isolates from market hogs (29.6%). C. jejuni isolates from both sources had lower MDR rates (8.4% for market hogs and 6.4% for sows). Isolates based on their MDR profiles were grouped into clusters by using an unsupervised machine learning algorithm. A large MDR cluster (n = 653) of C. coli isolates of market hogs was identified that included isolates that showed high resistance to lincosamides (99%), tetracyclines (89%), and macrolides (72%), moderate resistance to quinolones (25%), and low resistance to aminoglycosides (2%). A multivariable logistic regression model was constructed to assess the impact of predictor variables, sampling source (market hogs vs. sows), Campylobacter species (C. coli vs. C. jejuni), and year of sampling, on the likelihood of multidrug resistance (MDR) as the outcome. Higher odds of MDR were found in C. coli compared to C. jejuni isolates (OR = 4.00, 95% 2.24-7.92), in market hogs compared to sows (OR = 2.46, 95% CI: 1.99-3.06), and in 2014 compared to 2013 (OR = 1.51, 95% CI: 1.07-2.14). Production-type-specific antimicrobial stewardship strategies are needed to mitigate the health burden of multidrug-resistant Campylobacter spp.