Dynamics of Campylobacter spp. Contamination in Broilers from Farm-to-Slaughter Chain

Campylobacter jejuni and C. coli are leading causes of bacterial gastroenteritis worldwide, commonly linked to undercooked poultry. Within a One Health perspective, understanding their dissemination from farm-to-slaughterhouse is essential. This study aimed to detect Campylobacter spp. in intensively reared broiler chickens at critical points along the production chain and to assess antimicrobial resistance genes. Two production cycles, November to December 2024 and July to August 2025, were monitored weekly across three Portuguese poultry farms and a shared slaughterhouse. In total, 2164 samples were collected, including farm, transport, and slaughterhouse samples. Detection followed ISO 10272-1:2017 and 10272-2:2017 standards. Campylobacter prevalence peaked during weeks 3 and 4 on farms (9.4% cloacal, 23.5% litter). Transport crates showed contamination before/after loading (15.0%). At the slaughterhouse, contamination was low (8.3%) in process waters but high in neck skin samples (76.7%), with 15.2% exceeding the 1000 CFU/g limit (EU Regulation 2017/1495). Among 56 confirmed isolates, C. jejuni was most prevalent (46.4%), followed by C. coli (32.1%). The tetO gene was detected in most isolates (69.4%), while blaOXA-61 was less frequent (30.6%). Findings highlight the need for integrated control strategies, including improved biosecurity, crate sanitation, optimized processing procedures, systematic monitoring, and responsible antimicrobial use to enhance food safety and public health.