Microscopic spirochete counts in untreated subjects with and without periodontal tissue destruction

Highly conserved surface proteins of oral spirochetes as adhesins and potent inducers of proinflammatory and osteoclastogenic factors

Oral spirochetes include enormously heterogeneous Treponema species, and some have been implicated in the etiology of periodontitis. In this study, we characterized highly conserved surface proteins in four representative oral spirochetes (Treponema denticola, T. lecithinolyticum, T. maltophilum, and T. socranskii subsp. socranskii) that are homologs of T. pallidum Tp92, with opsonophagocytic potential and protective capacity against syphilis. Tp92 homologs of oral spirochetes had predicted signal peptides (20 to 31 amino acids) and molecular masses of 88 to 92 kDa for mature proteins. They showed amino acid sequence identities of 37.9 to 49.3% and similarities of 54.5 to 66.9% to Tp92. The sequence identities and similarities of Tp92 homologs of oral treponemes to one another were 41.6 to 71.6% and 59.9 to 85.6%, respectively. The tp92 gene homologs were successfully expressed in Escherichia coli, and the recombinant proteins were capable of binding to KB cells, an epithelial cell line, and inhibited the binding of the whole bacteria to the cells. Antiserum (the immunoglobulin G fraction) raised against a recombinant form of the T. denticola Tp92 homolog cross-reacted with homologs from three other species of treponemes. The Tp92 homologs stimulated various factors involved in inflammation and osteoclastogenesis, like interleukin-1beta (IL-1beta), tumor necrosis factor alpha, IL-6, prostaglandin E(2), and matrix metalloproteinase 9, in host cells like monocytes and fibroblasts. Our results demonstrate that Tp92 homologs of oral spirochetes are highly conserved and may play an important role in cell attachment, inflammation, and tissue destruction. The coexistence of various Treponema species in a single periodontal pocket and, therefore, the accumulation of multiple Tp92 homologs may amplify the pathological effect in periodontitis.

Molecular epidemiology of oral treponemes in patients with periodontitis and in periodontitis-resistant subjects

The etiologic role of oral treponemes in human periodontitis is still under debate. Although seen by dark-field microscopy in large numbers, their possible role is still unclear since they comprise some 60 different phylotypes, most of which are still uncultured. To determine their status as mere commensals or opportunistic pathogens, molecular epidemiological studies are required that include both cultured and as-yet-uncultured organisms. Here we present such data, comparing treponemal populations from chronic periodontitis (CP) or generalized aggressive periodontitis (GAP) patients. As a periodontitis-resistant (PR) control group, we included elderly volunteers with more than 20 natural teeth and no history of periodontal treatment and no or minimal clinical signs of periodontitis. Almost every treponemal phylotype was present in all three groups. For most treponemes, the proportion of subjects positive for a certain species or phylotype was higher in both periodontitis groups than in the PR group. This difference was pronounced for treponemes of the phylogenetic groups II and IV and for Treponema socranskii and Treponema lecithinolyticum. Between the periodontitis groups the only significant differences were seen for T. socranskii and T. lecithinolyticum, which were found more often in periodontal pockets of GAP patients than of CP patients. In contrast, no difference was found for Treponema denticola. Our findings, however, strengthen the hypothesis of treponemes being opportunistic pathogens. It appears that T. socranskii, T. lecithinolyticum and group II and IV treponemes may represent good indicators for periodontitis and suggest the value of the respective probes for microbiological diagnosis in periodontitis subjects.

Association of oral spirochetes from sites of periodontal health with development of periodontitis

The purpose of this investigation was to determine whether the presence of disease-associated bacteria in health-associated plaque correlated with susceptibility to periodontitis over time. Sites of periodontal health were identified in 65 adults. Six months later (recall 1), plaque was collected from sites that remained in periodontal health, and specific bacteria were detected using monoclonal antibodies in a microscopic assay. The spirochete morphogroup was identified by phase contrast microscopy. The relationship between detection at recall 1 and development of periodontitis over two successive 6-month intervals (recalls 2 and 3) was evaluated by means of logistic regression using generalized estimating equations (GEE), from which odds ratios (OR) were estimated and tested for significance. Significant relationships were defined as those having ORs with P < 0.05. Ninety-three of 1,032 sites developed signs of early periodontitis over the 12-month interval between recall 1 and recall 3. The spirochete morphogroup (OR = 3.13, P < 0.001) and pathogen-related oral spirochetes (PROS) (OR = 3.68, P < 0.001) were significantly associated with healthy sites that developed periodontitis. The association of Treponema socranskii was not significant (OR = 3.62, P = 0.0918). Odds ratios for Campylobacter rectus, Eikenella corrodens, and Porphyromonas gingivalis were less than 2.0 and not significant. Treponema denticola was not detected in health-associated plaque from stable health sites and was detected in only three sites that progressed to periodontitis. These findings indicate that the presence of PROS and some unidentified spirochetes in health-associated plaque is associated with increased susceptibility to periodontitis.

Environmental effects on the growth and proteolysis of Treponema denticola ATCC 33520

The effect of pH, redox potential, O2 and H2 on the growth and proteolytic activity of Treponema denticola ATCC 33520 was studied in a chemostat at different growth rates. The peptidase and protease activities were estimated using different amido-methyl coumarin derivatives and azocasein. The maximum growth rate of T. denticola ATCC 33520 was 0.14 h-1. Reduction of the growth rate of T. denticola by 50-60% gave: an increase in cell mass of 150-200%, a higher acetogenesis and a shift of the pH optimum. The protease and phenylalanine peptidase activities seemed to be of greater importance for the growth of T. denticola ATCC 33520 than the rather low arginine and proline peptidase activities. The redox potential (Eh) played a secondary role. At microaerophilic conditions with 1-5% O2, the cultures maintained a redox potential below -311 mV and an optimal acetogenesis. The presence of H2 induced a marked growth stimulation of T. denticola ATCC 33520. It is concluded that the cell mass and proteolytic activity of T. denticola ATCC 33520 are modulated by the growth rate and the pH and to a lesser extend by the redox potential and presence of O2. Stagnation of the exudate-flow influences these factors and will lead to an increase of the spirochetal population and proteolysis in the periodontal pocket.