Molecular Epidemiological Study of Periodontopathic Bacteria in Periodontal Diseases

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Previous epidemiological studies of Porphyromonas gingivalis(Pg)and Actinobacillus actinomycetemcomitans(Aa)in periodontal diseases have performed to analyze their clinical isolates from diseased periodontal regions by biotyping, serotyping, ribotyping and genotyping. These typing methods following by their bacterial culture and isolation are time-consuming and complicated. It is difficult to fully elucidate the microflora of individulas with periodontals diseases by analysing the limited number of clinical isolates. The aim of this study was to examine the direct identification of Pg and Aa in subgingival palque samples and further their genotyping based on the specific antigen genes amplified by polymerase chain reaction(PCR). In this study, the outer membrane protein(OMP)gene and fimbrial protein(FMP)gene were selected as the specific antigen gene for Pg and Aa, respectively. Our PCR method for specific antigen genes could allow the direct and specific detection of Pg and Aa in plaque samples. Pg were classified into two OMP genotypes(pga53 and pga67)by PCR and Aa were differenciated into four FMP genotypes by PCR-restriction fragment-length polymorphism(RFLP). We examined the distribution and prevalence of Pg and Aa genotypes in 59 patients(145 sites)with periodontal diseases. Almost of the patients were infected with only single genotype of Pg and/or Aa. In the case of two families(mother-son-daughter), the identical genotypes of Pg and Aa were distributed among family members. These results indicated that periodontal diseases might be initiated and progressed by clonal genotype of Pg and/or Aa, which might be possibly transmitted within family. The PCR-genotyping method based on specific antigen genes of Pg and Aa would be useful tools for their molecular epidemiological study in periodontal diseases and provide new insights into their transmission and pathogenesis.