The MoMIR-PPC project: The project aims to develop new approaches to predict, identify and prevent the appearance of animal and human super-shedders based on immune response and gut microbiota (GM) composition. The project focuses on four objectives. 1-Decipher why some animals become super-shedders or human become chronic carriers. 2-Identify immune and microbiota biomarkers to detect super-shedders and/ or prolonged carriers. 3-Define preventive and control measures by the characterisation of prebiotics, probiotics and nutraceutical products. 4-Develop mathematical models to provide new risk management tools and a pool of biosecurity measures at the farm levels. For this purpose, we have focused our research on Salmonella infections, which are an important economic and public health problem worldwide. Our INRA project: The development of a new infection model in isolator, where animal reinfections are greatly reduced, demonstrated that two main shedding phenotypes may emerge within a same chicken genetic background. Depending on the levels of Salmonella faecal excretion and caecal colonization levels, we may define the super- and low-shedder categories. In this project, we analysed the role of 1-gut microbiota, 2-immune status of chicks, 3-virulence of Salmonella strains. Metabarcoding characterization showed that GM composition before infection partly determined the levels of Salmonella colonization. Consistent with this idea, the transfer of GM, collected before infection from individuals that later developed the super-shedding syndrome yielded to the development of the super-shedder phenotype. In the same way, the transplantation of GM taken from adults, which are more resistant than chicks, can transfer resistance to Salmonella colonization. The analysis of GM composition before and after infection revealed significant differences among super and low-shedder chicks. In conclusion, some gut bacteria present before infection in low-shedder animals could be used as protective probiotics or as biomarkers. These results also suggest that Salmonella colonization is inhibited and/or promoted by a subset of microbes naturally found, before Salmonella colonization, in varying abundances within the GM.