Oral microbiome composition changes in mouse models of colitis

Background and Aim: Oral mucosal pathologies are frequent in inflammatory bowel disease (IBD). Since host-microbiome interactions are implicated in the pathogenesis of IBD, in this study the potential for changes affecting the oral microbiome was evaluated using two complementary mouse models of colitis: either chemically (dextran sulfate sodium) or with Citrobacter rodentium infection. Methods: After sacrifice, the tongue, buccal mucosa, saliva, colon, and stool samples were collected for analyses. Denaturing gradient gel electrophoresis was performed to assess bacterial 16S rRNA gene profiles. Relative changes were determined using quantitative polymerase chain reaction analysis for the phyla Bacteroidetes, Firmicutes, Spirochetes, and Actinobacteria, classes Gammaproteobacteria and Betaproteobacteria, and the genera Bacillus and Lactobacillus. These groups represent over 99% of the oral microbiota of healthy C57BL/6 mice. Results: Both models of colitis changed the oral microbiome, with the buccal microbiome being the most resistant to alterations in composition (maximum 1.8% change, vs tongue maximum 2.5% change, and saliva which demonstrated up to 7.2% total changes in microbiota composition). Changes in the oral microbiota were greater after dextran sulfate sodium challenge, compared with C.rodentium-induced colitis. Using cluster analysis, tongue and buccal mucosal microbiota composition changed ~5%, saliva ~35%, while stool changed ~10%. Conclusion: These findings indicate that dysbiosis observed in murine models of colitis is associated with changes in the composition of bacteria present in the oral cavity and in saliva. Such changes in the oral microbiota could be relevant to the etiology and management of oral mucosal pathologies observed in IBD patients.