Bacillus velezensis HBXN2020 alleviates Salmonella Typhimurium infection in mice by improving intestinal barrier integrity and reducing inflammation

Bacillus velezensis is a species of Bacillus that has been widely investigated because of its broad-spectrum antimicrobial activity. However, most studies on Bacillus velezensis have focused on the biocontrol of plant diseases, with few reports on antagonizing Salmonella Typhimurium infections. In this investigation, it was discovered that Bacillus velezensis HBXN2020, which was isolated from healthy black pigs, possessed strong anti-stress and broad-spectrum antibacterial activity. Importantly, Bacillus velezensis HBXN2020 did not cause any adverse side effects in mice when administered at various doses (1 x 107, 1 x 108, and 1 x 109 CFU) for 14 d. Supplementing Bacillus velezensis HBXN2020 spores, either as a curative or preventive measure, dramatically reduced the levels of Salmonella Typhimurium ATCC14028 in the mices feces, ileum, cecum, and colon, as well as the disease activity index (DAI), in a model of infection caused by this pathogen in mice. Additionally, supplementing Bacillus velezensis HBXN2020 spores significantly regulated cytokine levels (TNF-, IL-1{beta}, IL-6, and IL-10) and maintained the expression of tight junction proteins and mucin protein. Most importantly, adding Bacillus velezensis HBXN2020 spores to the colonic microbiota improved its stability and increased the amount of beneficial bacteria (Lactobacillus and Akkermansia). All together, Bacillus velezensis HBXN2020 can improve intestinal microbiota stability and barrier integrity and reduce inflammation to help treat infection by Salmonella Typhimurium.