Consequences of Campylobacter jejuni and Campylobacter coli Colonisation of Piglets on Gut Microbiota and Microbial Metabolites

Campylobacter (C.) jejuni and C. coli are common zoonotic bacteria in pigs, which typically act as asymptomatic carriers. However, the effects of Campylobacter colonisation on the porcine intestinal microbiota and metabolome remain poorly understood. This study investigated microbiome and metabolome alterations associated with co-colonisation by C. jejuni and C. coli in the different intestinal segments of pigs. Thirty-two weaned piglets were assigned to a control group and a group inoculated with C. coli ST5777/CT828 and C. jejuni ST122/CT206. Four weeks post inoculation, jejunal and caecal contents were analysed for Campylobacter counts, metabolite profiles and microbial composition. All animals remained clinically healthy. Both Campylobacter species colonised the jejunum and caecum, with higher C. coli counts in the caecum. Campylobacter-colonised pigs showed significantly altered metabolite profiles, including reduced cysteine and urea and increased glycine in the jejunum, as well as elevated 3-hydroxybutyrate levels in the caecum. In contrast, short-chain fatty acid concentrations in the caecum were unaffected by infection. Microbiota analysis revealed a significant reduction in caecal alpha diversity, whereas jejunal diversity remained unchanged. Infected pigs exhibited increased relative abundances of Lactobacillaceae and Bifidobacteriaceae and a decreased abundance of Pseudomonadota, including Enterobacteriaceae. In conclusion, Campylobacter co-colonisation induces distinct microbiome and metabolome alterations in pigs despite the absence of clinical disease. These findings highlight complex host-microbiota–pathogen interactions that may be relevant for future Campylobacter control strategies in pig production.