Co-inoculation of broilers by Campylobacter and Salmonella : effect on colonization, cecal microbiota, and serum metabolome

ABSTRACT Campylobacteriosis and salmonellosis are the leading bacterial zoonoses in Europe, with poultry meat being the primary source of human contamination. Although both Campylobacter and Salmonella bacteria can coexist asymptomatically in chickens, their reciprocal impact remains underexplored. An in vitro study showed that Campylobacter jejuni survival was positively affected by the presence of Salmonella , but no data are available on this interaction in the animal gut. In this study, an in vivo investigation was carried out to explore the dynamics between Campylobacter and Salmonella colonization in chickens. The results revealed that both Salmonella and Campylobacter maintained significantly higher levels of colonization in the ceca throughout the experiment when co-inoculated compared to when inoculated alone. Additionally, changes in the microbiota were associated with each pathogen inoculated alone, but the simultaneous presence of Campylobacter and Salmonella induced specific modulations that could possibly explain this phenomenon. Significant differences were found in the serum metabolome of the contaminated groups, and partial least squares discriminant analysis models enabled the discrimination of contaminated animals from controls using these metabolic signals. Furthermore, possible links between variations in the microbiota and variations in the metabolome were identified. IMPORTANCE This study demonstrates a synergistic effect between Salmonella and Campylobacter jejuni in the gut during co-infection in chickens, leading to an increased presence of both pathogens, as well as unique microbiota and metabolome changes. These findings underscore the importance of considering co-infection in poultry control measures and highlight the complex interplay between pathogens, microbiota, and metabolism.