Effects of Defined Pig Microbiota on Acute Salmonellosis in Gnotobiotic Piglets

Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) is a ubiquitous Salmonella serovar that causes enterocolitis in humans, livestock, poultry, and some pets. Gnotobiotic animals are suitable for studying the development of initial colonization in the gastrointestinal tract, host-microbiota cross-talk, and interactions among microbiota strains. To clarify the impact of pre-colonization of the germ-free piglets with defined pig microbiota (DPM) on the subsequent infection with S. Typhimurium LT2 (LT2), we focused on the acute host immune response. Colonization with DPM did not cause signs of enterocolitis (sleepiness, anorexia, fever, and diarrhea), histological changes in the intestine, the density of acid mucin-producing cells, expression of villin, claudin-1, occludin, TLR4, MD-2, CD14, LBP, MyD88, and TRIF, induction of inflammatory cytokines IL-1β, IL-6, IL-8, IL-10, IL-12/23p40, TNF-α, IFN-γ, and HMGB1. LT2 translocated into the mesenteric lymph nodes, liver, spleen, and blood of the LT2 group, as well as damaged the intestinal structure, and upregulated intestinal inflammatory cytokine levels. The pre-colonization with DPM ameliorated the LT2-induced signs of enterocolitis, intestinal damage, and inflammatory changes. Changes in intestinal levels of soluble TLR4 and TLR2 indicate the possible inclusion of soluble TLRs in the regulation of the inflammatory process. The controlled initial colonization of the newborn gastrointestinal tract with a defined microbial consortium can increase newborn resistance to enteric pathogens and promote thriving of young animals.