Detection of novel oral phylotypes associated with periodontitis.

A phylogenetic approach based on 16S rRNA (rDNA) has been recently applied to investigate the diversity of cultivable and uncultivable species in the human oral cavity without cultivation. In a previous study [Sakamoto et al. (2000) Microbiol. Immunol. 44, 643-652], we identified a number of novel oral phylotypes, representing as yet uncultured organisms. The purpose of this study was to design specific PCR primers for five phylotypes AP12, AP21, AP24, AP50, and RP58, which are deeply branched particularly in the phylogenetic tree, and determine the prevalence of these phylotypes in 45 patients with periodontitis and 18 healthy subjects. The specificity of each primer was validated by the sequence analysis of PCR products obtained from saliva and subgingival plaque samples. Among phylotypes tested, phylotype AP24, which is closely related to oral clone DA014 reported previously [Paster et al. (2001) J. Bacteriol. 183, 3770-3783], was significantly associated with saliva and subgingival plaque samples from patients with periodontitis (P<0.01), but the difference was not statistically significant in the presence of other phylotypes. These data suggest that phylotype AP24 may play an important role in periodontal disease.