Distribution of periodontopathic bacteria in tongue coats in aged subjects

Objective: Previously we reported that tongue coat could be a possible habitat of Porphyromonas gingivalis in aged subjects. In this study, we further investigated the frequency of the colonization of four periodontopathic bacteria in tongue coats from 85-year-olds and assessed the relationship to the periodontal status. Methods: The 165 (93 dentulous and 72 edentulous) volunteers aged 85 years participated in this study. After a clinical examination including Community Periodontal Index (CPI), the tongue coat was collected by scratching with a toothbrush and suspended in PBS. The DNA sample was prepared from the precipitate, and P. gingivalis, Prevotella intermedia, Tannerella forsythensis and Treponema denticola in tongue coats were detected by species-specific PCR methods. Results: Among four periodontopathogens, T. forsythensis (63.0%) was found most frequently, followed by P. gingivalis (50.3%) and T. denticola (37.6%), and P. intermedia (24.8%) was most infrequently detected. All of these bacterial frequencies were higher in the tongue coats from the dentulous subjects than those from the edentulous ones (all p < 0.001). Furthermore, the dentulous subjects with higher CPI (CPI code = 3 and 4) showed significantly higher frequency of colonization with P. gingivalis, P. intermedia and T. denticola than those with lower CPI (CPI code = 0 to 2) (p < 0.05). Conclusions: The four periodontopathic bacteria were detected in the tongue coats from not only dentulous but also edentulous subjects, suggesting that tongue coat could be a possible habitat of several periodontopathic bacteria. However, the frequencies of the colonization in edentulous subjects were significantly lower than those in dentulous subjects. Further, in the dentulous subjects, relatively higher frequencies of periodontopathic bacteria were observed in the higher CPI code group. Thus, it was suggested that the colonization of periodontopathic bacteria in tongue coats could be closely related to the periodontal status in aged subjects.