Subgingival spirochete diversity among healthy and chronic periodontitis subjects

Abstract

Numerous studies have demonstrated a strong association between oral spirochetes and periodontal disease. Molecular analyses of 16S rRNA gene sequences have shown that all oral spirochetes belong to the genus Treponema, of which there are 10 different ‘phylogroups'. Compared with healthy controls, diseased subjects have previously been shown to have greater diversity of subgingival treponeme species. However, a more detailed study is required to clarify this issue. Objectives: To compare the diversity of subgingival treponeme species among matched periodontally healthy and diseased subjects. Methods: Pooled subgingival plaque samples were collected from multiple deep pockets or sulci of five chronic periodontitis or periodontally-healthy subjects, respectively. Bacterial DNA was extracted and 16S rRNA genes were PCR-amplified using ‘treponeme-selective' primers. PCR products were cloned, and 50-60 clones from each subject were sequenced, to identify the ‘phylogroups' present. Results: In the periodontitis group, 65% of plasmid clones (179) contained treponeme 16S rRNA genes, which could be assigned to 8 different phylogroups. Sequence data from the healthy group indicated similar diversity of treponeme species. While the percentage of treponeme clones obtained was slightly lower (55%), all 8 groups present in diseased group could be found in healthy group. Group 1 treponemes (T. vincentii/T. medium) were the most abundant in both healthy (41%) and periodontitis subjects (45%). The majority of non-treponeme species identified were Deferribacteraceae, Flexistipes, Olsenella or Atopobium. Conclusions: Our results indicate there are no significant differences in the diversity of oral treponeme species in the sulcal/subgingival plaque of healthy or chronic periodontitis subjects.