Longitudinal Study of Tannerella forsythia prtH Genotype and Attachment Loss

Objectives: Tannerella forsythia has been designated as an important risk factor for developing destructive periodontal disease in adults.The prtH gene of T. forsythia has recently been shown to encode for a cysteine protease possessing virulent properties. The aim of this project was to examine the prevalence of the prtH genotype in an Australian population and to relate this with loss of attachment over a five-year period. Methods: The study population was drawn from participants in a five-year clinical study on the progression of periodontal disease on the basis that they had experienced attachment loss of ³2mm in ³2 sites during the five years (LOA+ group, n=35). A control group (LOA- group, n=36) consisting of persons of similar age and gender who had not experienced attachment loss was also selected. Clinical measurements and subgingival plaque samples were obtained at baseline and then at yearly intervals. Real-time PCR was used to detect the presence of the prtH gene in the plaque samples. The non-parametric Mann Whitney U test was used to determine whether there were any significant differences in the levels of the prtH genotype between the LOA+ and LOA- groups. Results: The prtH gene was detected on at least one occasion in almost every person infected with T. forsythia. Baseline levels of prtH were significantly lower in the LOA- group compared with those who lost attachment over either one, two, four or five years. In the LOA+ group, the higher prtH levels at baseline were not maintained through to the end of the observation period. Conclusion: Higher levels of the prtH genotype at baseline were significantly associated with future attachment loss. However, these higher levels were not necessarily maintained through the period of attachment loss.