Experimental Inoculation of Aggregatibacter actinomycetemcomitans and Streptococcus gordonii and Its Impact on Alveolar Bone Loss and Oral and Gut Microbiomes

Oral bacteria are implicated not only in oral diseases but also in gut dysbiosis and inflammatory conditions throughout the body. The periodontal pathogen ( ) often occurs in complex oral biofilms with ( ), and this interaction might influence the pathogenic potential of this pathogen. This study aims to assess the impact of oral inoculation with , , and their association ( + ) on alveolar bone loss, oral microbiome, and their potential effects on intestinal health in a murine model. and/or were orally administered to C57Bl/6 mice, three times per week, for 4 weeks. was also injected into the gingiva three times during the initial experimental week. After 30 days, alveolar bone loss, expression of genes related to inflammation and mucosal permeability in the intestine, serum LPS levels, and the composition of oral and intestinal microbiomes were determined. Alveolar bone resorption was detected in , , and groups, although bone levels did not differ from that of the SHAM-inoculated group. expression was upregulated in the group relative to the other infected groups, while expression was downregulated in infected groups. a or downregulated the expression of tight junction genes , , , and whereas infection with led to their upregulation, except for . was detected in the oral biofilm of the + group but not in the gut. Infections altered oral and gut microbiomes. The oral biofilm of the group showed increased abundance of , , and while administration enhanced the abundance of and . The gut microbiome of infected groups showed reduced abundance of . Infection with or disrupts both oral and gut microbiomes, impacting oral and gut homeostasis. While the combination of with promotes survival in the oral cavity, it mitigates the adverse effects of in the gut, suggesting a beneficial role of associations in gut health.