Characterization of Campylobacter isolates from chicken farms and retail poultry meat

Campylobacter is a major bacterial cause of gastroenteritis worldwide, and poultry meat is widely recognized as a principal reservoir for human Campylobacter infection. This study characterized the antimicrobial susceptibility profiles, genomic diversity, key antimicrobial-resistance determinants, and virulence genes of Campylobacter isolates collected from chicken farms and fresh retail poultry meat in ten regions of Jiangsu Province, China. The biofilm- forming capacity of selected strains was also evaluated. MLST identified CC-574 and CC-828 as the predominant clonal complexes of Campylobacter jejuni and Campylobacter coli, respectively. The isolates exhibited a broad range of sequence types (STs), including 21 previously documented STs in C. jejuni and 16 in C. coli, as well as six novel STs from C. jejuni and three novel STs from C. coli. Phylogenetic analysis revealed extensive genetic diversity among the Campylobacter isolates. Overall, 46.6 % of isolates were classified as MDR. The MDR proportion was significantly higher in C. coli (75.4 %) than in C. jejuni (17.5 %), and C. coli exhibited broader resistance across the ten antibiotics assessed. Among the detected resistance genes, the resistance-enhancing variant RE-CmeABC, which was primarily harbored by C. jejuni, had the highest prevalence (32.8 %), followed by tet(O) (31.3 %), the aminoglycoside resistance gene cluster aadEsat4-aphA-3 (21.9 %), and erm(B) (9.4 %). Virulence-gene profiling of the 128 Campylobacter isolates identified 10 virulence genes across five functional categories: adhesinon, invasion, immune modulation, motility, and toxin production. The wlaN gene, which is associated with Guillain-Barré syndrome, was detected in 7 (5.5 %) C. jejuni isolates. Among the 38 Campylobacter strains tested for biofilm formation, six C. coli isolates exhibited pronounce biofilm-forming capacity. These findings indicate that Campylobacter isolates from chicken farms and retail poultry meat pose potential public health risks, underscoring the need for targeted Campylobacter control strategies and providing a useful reference for future surveillance pograms.