Comprehensive detection of periodontal pocket bacterial flora and quantitation of disease-specific bacterial species

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Background : Nearly 400 species of bacteria have been found in the human periodontal pockets. Half of those are considered to remain not-yet-cultured to this date. Further characterization of the ecology of those not-yet-cultured species in the microflora should be done for establishment of microbiological diagnosis of periodontal infection. The purpose of this study is to know ecology of subgingival microflora of chronic periodontitis patients by sequence-based method for an approach to diagnosis in human periodontal microbial ecology.Methods : Four 16S rRNA gene libraries were constructed from subgingival plaque samples taken from all of diseased sites of 4 chronic periodontitis patients. The 480 clones from each libraries were analyzed by phylotyping.Results : The species richness contained a group of abundant shared species (17 phylotypes) and a group of individually diverse rare species (58〜83 phylotypes). Both groups consisted of〜25% of well-described and〜75% of not-yet-cultured phylotypes. The phylotypes were assigned to the Bacteroidetes, Fusobacteria, Proteobacteria, Firmicutes, Spirochetes, Actinobacteria, and TM7 phyla. Previously reported periodontally associated species and phylotypes were found in some samples but not to be shared by all. Diverse sub-phylotypes showing more than 99% of sequence similarity showed individually skewed distribution.Conclusions : The species richness and abundance of the not-yet-cultured species seemed to be 70-80% and 70-80% respectively in subgingival microflora. However most of those phylotypes were phylogenetically close to well-described periodontally associated bacteria. Individual differences were found in patchness of the species within not-yet-cultured as well as well-described species of the microflora. These individually distinct patchy distributions are expectable to serve microbial diagnosis for 'tailor-made' periodontal treatment.