Oral treponeme phylotypes associated with periodontal health and diseas

Abstract

OBJECTIVES: There are 10 human oral treponeme ‘phylogroups’, each composed of various numbers of treponeme species and/or species-level phylotypes. The objective of this study was to analyze the composition of treponeme phylotypes present in periodontal niches in subjects with periodontitis versus healthy controls. METHODS: After scrupulous removal of supragingival plaque, pooled subgingival plaque was sampled from multiple sites from 10 periodontitis patients and 10 periodontitis-free controls. The periodontal health status was clinically assessed using standard criteria (including %BOP, %PPD 4-5mm and >6mm). Bacterial DNA was purified from each sample, and 16S rRNA genes were PCR-amplified using ‘treponeme-selective’ primers. Cloned 16S rRNA-gene libraries were constructed, and ca. 50 clones were sequenced for each subject. Treponeme species and phylotype diversity was systematically analyzed using bioinformatic, computational phylogenetic and statistical clustering methods. RESULTS: There was no statistically-significant difference in the number of 16S rRNA plasmid clones obtained from the periodontitis (n=510) and control (n=520) groups. Higher numbers of treponeme clones were obtained from the periodontitis subjects (n=365, 70.2%) versus periodontitis-free controls (n=250, 49.0%; p<0.05, Mann-Whitney U test). 7 out of 10 treponeme phylogroups were detected in both subject groups. Periodontitis subjects had a higher clonal abundance of phylogroup 2 treponemes (p<0.001). Two specific phylotypes from phylogroup 2, including one phylotype corresponding to the type strain of Treponema denticola, appear to be associated with periodontitis (p<0.01). There were significant differences in the composition of treponeme phylotypes detected in the periodontitis and control groups, with subjects clustering according to their clinical periodontal condition. CONCLUSIONS: A wide variety of treponeme species and (species-level) phylotypes are present in ‘healthy’ subgingival plaque. Specific bacterial lineages of phylogroup 2 treponemes have an increased association with periodontal disease.