Induction of Gut Dysbiosis and Turbulence of Intestinal Immune System by Oral Bacteria

Objectives: Growing evidence suggests an association between the dysbiosis of the gut microbiota with the pathogenesis of both intestinal and extra-intestinal disorders such as inflammatory bowel disease, allergy, asthma, metabolic syndrome, cardiovascular disease, and obesity. In this study, we assessed the potential effect of oral bacteria on the composition of the gut microbiota and the metabolic by-products, as well as the immune cell population in the small intestine in mouse model.

Methods: The microbiota in feces was analyzed using PCR and 16S ribosomal RNA sequencing. The metabolic by-products in feces were analyzed byhigh performance liquid chromatography.Th17/Treg populations and M1/M2 macrophage populations was analyzed by flow cytometry.
Results: Swallowing of oral bacteria (Streptococcus mitis, S. salivarius, Porphyromonas gingivalis, and Prevotella nigrescens) for 3 weeks caused gut dysbiosis, as it led to increase in Bacteroides and Staphylococcus,and decrease in Lactobacillus spp, although there were differences in theratio of intestinal flora between oralbacterial species.Furthermore, oral bacterial infection caused an increase in lactic acid and decrease in n-butyric acid. In the small intestine, imbalance of Th17/Treg cells and M1/M2 macrophages, and decreased IgA antibody production was recognized.
Conclusions: These results suggest that gut dysbiosis caused by swallowing of excessive oral bacteria, promotes decline in the intestinal mucosal immune response followed bychronic inflammation.