Distribution of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia in an Australian population

Background, aim: The present study describes (i) the natural distribution o f the three putative periodontopathogens Porphyromonas gingivalis, Prevotel la intermedia and Actinobacillus actinomycetemcomitans in an Australian pop ulation and (ii) the relationship between these organisms, pocket depths an d supragingival plaque scores. Methods: Subgingival plaque was collected from the shallowest and deepest p robing site in each sextant of the dentition. In total, 6030 subgingival pl aque samples were collected from 504 subjects. An ELISA utilising pathogen- specific monoclonal antibodies was used to quantitate bacterial numbers. Results:: A. actinomycetemcomitans was the most frequently detected organis m (22.8% of subjects) followed by P. gingivalis and P. intermedia (14.7% an d 9.5% of subjects respectively). The majority of infected subjects (83%) w ere colonised by a single species of organism. A. actinomyceteincomitans pr esence was overrepresented in the youngest age group but under-represented in the older age groups. Conversely, P. gingivalis and P. intermedia presen ce was under-represented in the youngest age group but over-represented in the older age groups. Differing trends in the distribution of these bacteri a were observed between subjects depending upon the site of the infection o r whether a single or mixed infection was present; however, these differenc es did not reach significance. Bacterial presence was strongly associated w ith pocket depth for both A. actinomyceteincomitans and P. gingivalis. For A. actinomycetemcomitans, the odds of a site containing this bacterium decr ease with deeper pockets. In contrast, for P. gingivalis the odds of a site being positive are almost six times greater for pockets >3 ram than for po ckets less than or equal to3 nun. These odds increase further to 15.3 for p ockets deeper than 5 mm. The odds of a site being P. intermedia positive we re marginally greater (1.16) for pockets deeper than 3 mm. Conclusions: This cross-sectional study in a volunteer Australian populatio n, demonstrated recognised periodontal pathogens occur as part of the flora of the subgingival plaque. Prospective longitudinal studies are needed to examine the positive relationship between pocket depth and pathogen presenc e with periodontal disease initiation and/or progression.