Key role of the gut microbial composition in the occurrence of Salmonella super‐and low‐shedder phenotypes in chicken

International audience

English. Heterogeneous shedding levels have been described in the many infectious diseases. Indeed, individual hosts that shed high levels of a given pathogen are of crucial importance for control strategies. However, much remain to be done to understand the mechanisms leading to high shedding. To study this phenomenon, we have developed of a new chicken infection model. The animals were reared in isolator, with devices allowing to greatly reduce animal reinfections. Under these conditions, we have observed that the two extreme Salmonella Enteritidis shedding phenotypes may emerge in chicken presenting the same genetic background. Based on the Salmonella faecal excretion and caecal colonization levels, these phenotypes were designated as super- and lowshedder. In this project, we have shown evidence of a relationship between the gut microbiota composition and the levels of Salmonella excretion : (1) germ-free and antibiotic-treated chicks are more prone to become super-shedders (2) super or low-shedder phenotypes can be acquired through microbiota transfer (3) specific gut microbiota taxonomic features, present in healthy animals before Salmonella inoculation, influence the development of a Salmonella low- and super-shedder phenotype (4) lower faecal excretion phenotype can be conferred by inoculation of four commensal bacteria prior to Salmonella infection. In conclusion, these results showed that Salmonella intestinal colonization is inhibited and/or promoted by a subset of bacteria naturally found, before Salmonella colonization, in varying abundances within the gut microbiota. Thus, some gut bacteria present before infection in lowshedder animals could be used as protective probiotics or as biomarkers. This paves the way for targeted interventions aiming at controlling Salmonella infection through a modulation of the gut microbiota.