The prtH-gene of Tannerella forsythensis is not associated with periodontitis

Methods: From a group of 68 consecutive adult periodontitis patients (mean age: 47,6 ± 10.1 yrs) the subgingival microflora was analysed for diagnostic purposes. From these patients, 33 patients harbouring T. forsythensis were selected to investigate the presence of the prtH-gene which encodes for a cystein proteinase. From each patient T. forsythensis was isolated from a subgingival plaque sample and determined by biochemical tests and a species-specific PCR reaction. The presence of the prtH-gene on the genome of the isolated strains was determined by PCR as described by Saito et al. (1997). To investigate the association of this gene with periodontitis, a group of 14 age-matched subjects (mean age: 56,4 ± 6.9 yrs) without any signs of periodontal disease (pocket depths < 3 mm, no attachment loss on radiograph). To exclude false-negative results because of selecting prtH-gene negative T. forsythensis isolates from the primary cultures, crude subgingival plaque was also used as a template source.

Results: In the group of 33 -positive patients we found two T. forsythensis isolates that were prtH-negative. From the crude subgingival plaque samples only 17 (with a maximum of 31) were positive for this gene despite repeated analyses. The T. forsythensis isolates from the 14 periodontal healthy subjects were all prtH-positive.

Conclusions: Based on our data the odds ratio of the presence of the prtH-gene in T. forsythensis in periodontitis patients versus healthy controls is 1.06 (p>>0.05). Therefore we conclude that the presence of the prtH-gene in T. forsythensis is not discriminative for patients with T. forsythensis-associated periodontitis when compared to healthy carriers of T. forsythensis.