Campylobacter multi‐locus sequence types and antimicrobial susceptibility of broiler cecal isolates: A two year study of 143 commercial flocks

The objective of this study was to assess genetic diversity and antimicrobial susceptibility of Campylobacter jejuni and coli from broiler ceca. Ceca from one broiler were collected from a commercial processing plant, once or twice weekly for 2 years (n = 143). Campylobacter were cultured from the cecal contents and analyzed by whole genome sequencing, multi‐locus sequence typing (MLST) and antimicrobial susceptibility testing. Seventy‐two of 143 carcasses examined were positive for Campylobacter. A total of 24 MLST sequence‐types (ST) were identified belonging to ten Campylobacter clonal complexes (CC). Three MLST clonal complexes, CC‐353 (53.2%), CC‐828 (17.7%), and CC‐48 (11.4%) accounted for the majority of Campylobacter isolates recovered. Compared to all other clonal complexes, a significantly higher percentage (p < .05) of C. coli isolates belonging to CC‐828 complex were resistant to azithromycin, clindamycin, erythromycin, and gentamicin. CC‐48 was significantly more resistant to ciprofloxacin and nalidixic acid than other CCs regardless of species. No isolates were resistant to florfenicol. Practical applications Despite high genetic diversity among Campylobacter recovered from broiler ceca during this 2‐year study, antimicrobial resistance was significantly linked to MLST clonal complex, specifically C. coli, CC‐828 and C. jejuni, CC‐48.