S. Mutans Effects On Gut Microbiota Of Mice

To investigate the effects of Streptococcus mutans on intestinal tissues and intestinal flora in healthy mice and mice with ulcerative colitis (UC), elucidating the potential correlation between cariogenic microorganisms and intestinal diseases. C57BL/6 mice were divided into healthy and UC groups. According to the administration of different doses of S. mutans, aminals are subdivided into S. mutans-20d and S. mutans-40d groups. All groups were monitored for weight, defecation, and disease activity index (DAI). Colons were harvested at 4 weeks post administration. Histopathological changes of intestinal tract was observed, and histological damage index (TDI) was assessed. The IL-17 and IFN-γ levels in peripheral blood was detected . 16S rRNA sequencing was performed to analyze the changes of intestinal flora. In healthy mice, S. mutans gavage induced progressive intestinal inflammation (elevated TDI/IL-17/IFN-γ) accompanied by α-diversity reduction and β-diversity alterations. Notably, 40d S. mutans gavage elevated Firmicutes/Bacteroidetes (F/B) ratio while promoting beneficial bacteria enrichment. In UC mice, S. mutans gavage exacerbated intestinal inflammation (elevated DAI/TDI/IL-17/IFN-γ). In addition, S. mutans gavage induced microbiota dysbiosis, characterized by reduced α-diversity, altered β-diversity, and a 40-day-specific elevation in the F/B ratio. Taxonomic analysis revealed S. mutans-40d enrichment of pathogenic taxa (g_Ileibacterium/g_Candidatus_Soleaferrea) and S. mutans-20d enrichment of beneficial taxa (g_Ligilactobacillus). S. mutans induced intestinal inflammation and microbiota dysbiosis in both models but with context-dependent effects, healthy mice showed probiotic enrichment, whereas UC mice exhibited pathogenic shifts.