Contribution of periodontal pathogens on tongue dorsa analyzed with real-time PCR to oral malodor

Oral malodor is considered to originate primarily from tongue microbiota populations. However, the relationship between oral malodor and tongue microbiota remains unclear. In this study, tongue periodontal pathogens were analyzed via real-time PCR, and the association between oral malodor and tongue periodontal pathogens, including Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia, Prevotella nigrescens and Treponema denticola, was examined. The subject population consisted of 29 individuals with and 10 healthy persons without oral malodor. Oral malodor was assessed by organoleptic test and volatile sulfur compound (VSC) levels as measured by gas chromatography. Real-time PCR was conducted for anaerobes in tongue biofilm samples employing a LightCycler system; furthermore, bacterial proportion served as a quantitative parameter. Among the five anaerobes, only T. forsythia displayed higher proportions in malodor subjects than corresponding values in healthy controls. Proportions of P. intermedia and P. nigrescens correlated strongly with hydrogen sulfide concentration. Proportions of P. gingivalis and P. nigrescens also exhibited strong correlation with methyl mercaptan concentration. The correlation coefficient between the proportion of the total of the five anaerobes and total VSC level (r = 0.88) was greater than that between bacterial proportion and organoleptic score (r = 0.29). When a linear regression analysis was performed utilizing the proportion of each of the five periodontal pathogens as an independent variable, the explanatory power of these independent variables revealed 81% for total VSC level and 16% for organoleptic score. These results suggest that these five periodontal pathogens on tongue dorsa may contribute greatly to VSC production.