A specific Streptococcus mutans strain aggravates non-alcoholic fatty liver disease

Objective: Streptococcus mutans, a major dental caries pathogen, has shown to be associated with the aggravation of cerebral hemorrhage and inflammatory bowel diseases. In this study, we evaluated the effects of S. mutans on the development of non-alcoholic steatohepatitis (NASH) in a mouse model. Materials and methods: Streptococcus mutans oral strain MT8148 (serotype c) and a blood isolate TW871 (k) were used. C57BL/6J mice (6 weeks old) were fed a high-fat diet for 4 weeks; the test strains or phosphate-buffered saline was then intravenously administered. Mice were euthanized after 8 or 12 weeks. Whole body, extirpated liver, and visceral fat weights were determined, and histopathological evaluations of the liver specimens were performed. Results: Mice infected with TW871 showed significantly greater body and liver weights than those administered MT8148 or phosphate-buffered saline. Histopathological analyses revealed prominent infiltration of inflammatory cells and adipocellular deposition in livers extirpated 8 weeks after an infection with TW871; fibrosis was also observed in livers extirpated after 12 weeks. Conclusion: These results suggest that a specific strain of S. mutans could induce NASH.