Bacterial composition of overall oral microbiota associated with periodontal disease and health.

Abstract: Oral cavity is colonized by numerous and diverse commensal microorganisms, which constitute complex microbial communities on various intraoral surfaces. Of them, plaque microbiota that forms on the tooth surfaces and gingival crevices are the cause of one of two major oral diseases, or periodontitis. Currently, little doubt exists that three subgingival plaque bacteria including Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola are prime suspects in periodontitis. Furthermore, recent studies using open-ended molecular approaches and the 16S rRNA gene have identified additional species, including Filifactor alosis as the periodontitis-associated taxa. Nevertheless, the bacterial etiology of periodontitis remains unclear, because the onset and progression of periodontitis cannot be simply explained by presence or absence of these taxa. To obtain deeper insights into oral microbiota composition associated with periodontal disease and health, we conducted a large-scale population-based study of oral microbiota composition using saliva. An important finding was that high bacterial richness in the microbiota constituted by various minority bacteria mainly derived from subgingival sites was significantly associated with gingival inflammation and periodontitis. Another important result was that relative abundances of predominant commensals were significantly associated with the health conditions. Of the two different cohabiting groups of predominant commensals mainly derived from tongue dorsum, a greater relative abundance of group II bacteria such as Neisseria flavescens and Porphyromonas pasteri, and Fusobacterium periodonticum was associated with better health conditions. We introduce our finding on the overall structure of the oral microbiota associated with gingival health obtained by our molecular epidemiological studies.