Comparison of the oral bacterial flora in saliva from a healthy subject and two periodontitis patients by sequence analysis of 16S rDNA libraries

The oral bacterial flora in the saliva from two patients with periodontitis and from a periodontally healthy subject were compared using a sequence analysis of 16S rDNA libraries without cultivation. 16S rDNAs were amplified from salivary DNA by PCR and cloned. Randomly selected clones were partially sequenced. On the basis of sequence similarities, the clones were classified into several clusters corresponding to the major phylum of the domain Bacteria. The major phylum in the libraries was the low G+C Gram-positive bacteria. There was no clonal sequence affiliated with periodontopathic bacteria in the salivary sample from the healthy subject, while a number of periodontal pathogens such as Campylobacter rectus, Prevotella intermedia, Porphyromonas gingivalis and Treponema socranskii were detected in the salivary samples from the patients with periodontitis. In addition, a number of previously uncharacterized and uncultured microorganisms were recognized. These organisms may have some role in periodontal disease. This study reveals some potential for a molecular-biological technique to analyze the oral microflora associated with periodontal disease, including previously uncharacterized and uncultured microorganisms, without cultivation.