<i>Bacillus velezensis</i> HBXN2020 alleviates <i>Salmonella</i> Typhimurium infection in mice by improving intestinal barrier integrity and reducing inflammation.

Abstract

<i>Bacillus velezensis</i> is a species of <i>Bacillus</i> that has been widely investigated because of its broad-spectrum antimicrobial activity. However, most studies on <i>B. velezensis</i> have focused on the biocontrol of plant diseases, with few reports on antagonizing <i>Salmonella</i> Typhimurium infections. In this investigation, it was discovered that <i>B. velezensis</i> HBXN2020, which was isolated from healthy black pigs, possessed strong anti-stress and broad-spectrum antibacterial activity. Importantly, <i>B. velezensis</i> HBXN2020 did not cause any adverse side effects in mice when administered at various doses (1×10⁷, 1×10⁸, and 1×10⁹ CFU) for 14 days. Supplementing <i>B. velezensis</i> HBXN2020 spores, either as a curative or preventive measure, dramatically reduced the levels of <i>S.</i> Typhimurium ATCC14028 in the mice's 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 <i>B. velezensis</i> HBXN2020 spores significantly regulated cytokine levels (<i>Tnfa</i>, <i>Il1b</i>, <i>Il6</i>, and <i>Il10</i>) and maintained the expression of tight junction proteins and mucin protein. Most importantly, adding <i>B. velezensis</i> HBXN2020 spores to the colonic microbiota improved its stability and increased the amount of beneficial bacteria (<i>Lactobacillus</i> and <i>Akkermansia</i>). All together, <i>B. velezensis</i> HBXN2020 can improve intestinal microbiota stability and barrier integrity and reduce inflammation to help treat infection by <i>S.</i> Typhimurium.