Prevalence and Characterization of Campylobacter Species Isolated from U.S. Swine: 2021 NAHMS Enteric Study

While Campylobacter species are often considered normal gastrointestinal commensal bacteria in many food animals, some species may cause gastrointestinal or reproductive diseases in swine. The U.S. swine industry lacks recent Campylobacter species prevalence estimates, which are useful in animal and public health management recommendations. This study describes the prevalence and characteristics, including antimicrobial resistance (AMR) of Campylobacter species as part of the National Animal Health Monitoring System (NAHMS) Swine 2021 study. Campylobacter species were isolated using culture-based methods, and antimicrobial susceptibility was determined by broth microdilution. Conventional polymerase chain reaction (PCR) was used to detect common AMR genes in isolates resistant to tetracycline, ciprofloxacin, and nalidixic acid. The Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR) was used to assess clonality. A total of 1,043 fecal samples were collected from 39 swine operations. Campylobacter species were detected in 321/1,043 samples (30.8%) and on 32 of 39 operations (82%); two different species were recovered from one sample, yielding 322 isolates. Campylobacter species included C. coli (309/322; 96%) and C. hyointestinalis (13/322; 4%). Six isolates failed to remain viable after storage, yielding 316 for AMR testing. Regardless of species, resistance was most often observed to tetracycline 282/316 (89.2%). Multidrug resistance (MDR to ≥3 drug classes) was observed in 110/316 isolates (51.9%). The tetO gene, determined from isolates prior to storage, was commonly seen (285/322; 88.5%) across all isolates. The ERIC-PCR indicated some clonality by swine operation site but overall lacked the sensitivity to broadly describe the population structure.