Introduction: Fusobacterium nucleatum, which is involved in the development of periodontal disease and apical lesions, can be transmitted to the colon and metastasize to colorectal cancer, suggesting a link between oral and systemic diseases. We analyzed the effects of F. nucleatum on bacterial flora in the gut and surrounding organs in a rat model of apical periodontitis and analyzed the infection route to the gut and distant organs.
Methods: We induced apical periodontitis in rat molars by infecting the dental pulp with F. nucleatum and then took X-ray images and performed histopathologic analyses. Next, we removed the maxilla, gut, heart, liver, and kidney from the rats at 0, 2, 4, and 8 weeks postsurgery and then extracted DNA samples and performed polymerase chain reaction and microbiome analyses using the Illumina MiSeq (Illumina Co, Tokyo, Japan).
Results: The presence of inflammatory cell infiltration confirmed apical periodontitis from 2-8 weeks. Polymerase chain reaction and microbiome analyses revealed F. nucleatum in the rat gut from 2 weeks and in the kidney from 8 weeks. The rat gut, heart, liver, and kidney exhibited altered bacterial flora, including a marked decrease in Verrucomicrobia and an increase in Proteobacteria after 2 weeks and increases in Bacteroidetes and Firmicutes after 4 weeks.
Conclusions: The onset of F. nucleatum-induced apical periodontitis changed the bacterial flora in the rat gut, heart, liver, and kidney, with a confirmed progressing infection in the large intestines.
Keywords: Fusobacterium nucleatum; apical periodontitis; gut flora; microbiome analysis.
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