Gut microbiota signatures associated with the development of Salmonella Typhimurium super-shedders in broiler chickens.

Broiler chickens infected with Salmonella Typhimurium (S. Typhimurium) may transition from acute infection to a persistent carrier state, with a subset of individuals becoming super-shedders that disproportionately contribute to pathogen dissemination within poultry flocks. However, the microbial and host factors driving the emergence of this phenotype remain poorly understood. In this study, birds were orally challenged with S. Typhimurium and stratified into high-, moderate-, and low-shedding groups based on fecal shedding dynamics. Birds that continuously excreted high bacterial loads (> 10⁵ CFU/g feces) at 14 days post-challenge (dpc) were defined as super-shedders. Persistent shedding was associated with impaired intestinal morphology, reduced production performance, and sustained intestinal inflammation. Full-length 16S rRNA sequencing revealed distinct fecal microbiota configurations among shedding phenotypes, with super-shedders characterized by a significant enrichment of Blautia and depletion of Escherichia and Streptococcus. Correlation analyses indicated that Blautia abundance was positively associated with fecal S. Typhimurium loads, whereas Escherichia showed a negative association. Furthermore, in vitro co-culture assays demonstrated that fecal supernatants from super-shedders promoted S. Typhimurium growth at later stages of incubation. Collectively, these findings suggest that a dysregulated gut microbiota and inflammation-driven intestinal microenvironment jointly facilitate the persistence and super-shedders of S. Typhimurium in broilers. Targeting gut microbial composition and intestinal inflammation may represent effective strategies to mitigate the emergence of super-shedders in poultry production.