Abstract
Background/Aims: The gut microbiota plays a crucial role in the pathogenesis and treatment of inflammatory bowel diseases (IBD). This study aimed to investigate the effects of active, heat-inactivated, and cell-free supernatant (CFS) forms of Bacteroides thetaiotaomicron, alone or in combination with infliximab, in dextran sodium sulfate (DSS)-induced colitis in mice. Colitis was induced by oral administration of DSS for seven days. B. thetaiotaomicron in its various forms was orally administered at a dose of 1 × 108 CFU prior to and during colitis induction. Infliximab was intraperitoneally injected from days 3 to 5 of DSS exposure. Colitis severity, gene expression, tumor necrosis factor alpha levels, and gut microbiota were assessed by disease activity index, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), and qPCR, respectively.Results: Active B. thetaiotaomicron and its CFS form significantly alleviated colitis symptoms compared to the heat-inactivated form. Furthermore, co-administration of active B. thetaiotaomicron and infliximab significantly modulated the colonic mRNA expression of Ocln, Tff3, Muc2 (upregulated), and Ace2 (downregulated). This combination also exhibited synergistic improvement in colitis severity in treated mice.Conclusions: These findings underscore the therapeutic potential of B. thetaiotaomicron in IBD, either alone or in combination with infliximab, and support further development of microbiota-based strategies for IBD prevention and treatment.