Quantitation of periodontal pathogens in subgingival plaque by real-time PCR

Chronic periodontitis is a bacterial associated inflammatory disease, resulting in destruction of the supporting tissues of the teeth, affecting approximately 35% of the adult population. Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia (formerly Bacteroides forsythus) have been implicated as pathogens associated with chronic periodontitis. Objectives: To determine the bacterial species composition of subgingival dental plaque during the clinical progression of periodontal disease. Methods: Forty one subjects with chronic periodontitis who were on a maintenance program completed the study. Clinical measurements and subgingival plaque samples were taken from five sites in each subject at 3 monthly intervals for 12 months. Disease progression was determined by assessment of clinical attachment loss as recorded by a Florida probe. 51% of subjects experienced disease progression indicated by >/=2 mm of clinical attachment loss during the course of the study. Real-time PCR was used to determine the relative proportions of P. gingivalis, T. denticola and T. forsythia and also total bacteria in subgingival plaque from 475 plaque samples. Results: T. forsythia was the most prevalent species, found in 81% of subjects, followed by T. denticola (68%), and P. gingivalis (54%). Positive correlations were found between pocket depth and each of the three species and also between each of the three species, with P. gingivalis and T. denticola rarely found in the absence of T. forsythia. Three months prior to disease progression being clinically detectable, the proportion of T. forsythia was significantly higher in sites that experienced disease progression compared with sites that were stable. Conclusion: T. forsythia may act as a predictor of disease progression. Project supported by NH&MRC Grant No. 219189.