Inoculation of four commensal bacteria in chicken has an impact on the gut microbiota composition, Salmonella colonisation and the immune response

International audienceAim: Many studies have revealed the importance of heterogeneous shedding levels in the context of infectious diseases. Individual hosts that excrete higher levels of pathogens (so-called super-shedders) are key targets for control strategies. However, the mechanisms associated with the emergence of super-shedders remain largely unknown. The development of a new infection model for chickens reared in isolator, where animal reinfections are greatly reduced, has allowed us to demonstrate that two main Salmonella Enteritidis shedding phenotypes can emerge within the same chicken genetic background. These phenotypes were designated as super- and low-shedder on the levels of Salmonella faecal excretion and caecal colonization. Methods and results: In this project, we analysed the parameters that could be responsible for these phenotypes, namely: 1- the modification of the virulence of the Salmonella strain during the asymptomatic carrier state ; 2- the faecal and caecal microbiota composition ; 3- the immune status of chicks measured in kinetic in blood. We also analysed the impact on these parameters of four commensal bacteria inoculated before infection. Conclusions: The data obtained showed the protective effect of the four commensal bacteria on Salmonella excretion and their major impact on gut microbiota composition and immune response