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Salmonellais recognized as an important foodborne pathogen, which seriously threatens human safety. Bacillus coagulansT242 (T242) could prevent the growth of Salmonellaand alleviate Salmonellainfection in Caco-2 cells in vitro. The main objective of this study was to investigate the mechanism of action of T242 in preventing Salmonellainfection in mice. Both T242 vegetative cells and spore prevention groups could reduce the bacterial loads in the ileum, liver and spleen of Salmonella typhimurium(S. typhi) SL1344 infected mice, and reduce the levels of Interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α) in serum and also increase the expression of Interleukin-1β (IL-1β) in serum, Monocyte chemoattractant protein-1 (MCP-1) and Inducible nitric oxide synthase (iNOS) in the liver, Interleukin-22 (IL-22) and Interleukin-23 (IL-23) in the ileum, and tight junction proteins (Claudin-1, Occludin and ZO-1) in the colon, and regulate intestinal flora. Pretreatment of T242 spores could downregulate the relative abundance of Desulfovibrionaceae in Salmonellainfected mice. The relative abundance of Ruminococcus in Salmonella-infected mice was down-regulated by T242 vegetative cells preconditioning. The results showed that T242 prevented the systemic spread of Salmonellaby regulating intestinal flora and enhancing intestinal barrier function against Salmonellainvasion, inducing anti-inflammatory effects and regulating immune responses. T242 had great potential in controlling the epidemic of foodborne pathogens and was expected to be an effective alternative to antibiotic therapy, which is of great significance for the control and defense of Salmonellainfection.

This study aimed to investigate the antibacterial activity of Bacillus coagulans(B. coagulans) T242 and its ability to alleviate the infection of Caco-2 cells with SalmonellaTyphimurium (S.Typhimurium) SL1344. B. coagulansT242 has a broad spectrum of the antibacterial activity. The cell-free supernatants of B. coagulansT242 inhibited the growth of S.Typhimurium SL1344 and changed its cell morphology. B. coagulansT242 inhibited the adhesion and invasion of S.Typhimurium SL1344 to Caco-2 cells by adhering to Caco-2 cells, significantly reduced the production of interleukin-6 (IL-6), Interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α) which induced by S.Typhimurium SL1344, also increased interleukin-10 (IL-10) production, thereby alleviating the inflammatory response of Caco-2 cells. B. coagulansT242 vegetative cells and spores could alleviate the decreased expression of tight junction proteins (Claudin-1, Occludin and ZO-1) caused by S.Typhimurium SL1344 infection in Caco-2 cells by increasing the expression of Claudin-1, Occludin and ZO-1. This study demonstrated that B. coagulansT242 could protect Caco-2 cells by adhesion, reducing inflammatory response and enhancing intestinal barrier function. Therefore, B. coagulansT242 will hopefully be an effective alternative to antibiotics, and this study has important implications for food safety issues.