Subgingival Distribution of Periodontal Pathogenic Microorganisms in Adult Periodontitis

The association between specific plaque microorganisms and periodontal diseases has been the subject of much recent interest due to its potential importance in the diagnosis and classification of these diseases. In order to optimize microbiological tests in periodontal therapy, it is important to know how many subgingival plaque samples must be assayed from a single patient in order to ascertain infection with a periodontal pathogen. To answer this question the present study assessed the distribution of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Bacteroides forsythus, and Prevotella intermedia in multiple subgingival plaque samples. The samples were quantitatively assessed for specific bacteria by indirect immunofluorescence, a technique previously found to correlate well with cultural assessment of these same organisms. Subgingival plaque from the mesial pockets/sulci of all teeth except third molars was sampled in 12 patients with adult periodontitis, 22 to 28 sites/patient for a total of 315 samples. These patients demonstrated an average mesial probing depth and loss of attachment of 3.7 ± 1.2 mm and 3.1 ± 1.5 mm, respectively (mean ± SD). P. gingivalis, P. intermedia, and B. forsythus were demonstrated in one or more sites from all patients, while A. actinomycetemcomitans was found in one or more sites in 8 of 12 patients. The proportion of positive sites per subject varied, but it was, on average, similar for the 3 blackpigmented organisms and ranged from 44% to 54%. In contrast, A. actinomycetemcomitans was identified, on average, in only 11.4% of the sites in these same patients. Based on these prevalence rates and association with certain clinical measures, it is recommended that 6 or more random sites from adult periodontitis patients or 4 or more sites with probing pocket depth ≥5 mm be sampled in order to detect P. intermedia and 25 or more random sites to detect A. actinomycetemcomitans at a 95% confidence level. Six or more random sites or 3 or more subgingival sites with probing pocket depth ≥ 5 mm need to be sampled in order to detect B. forsythus or P. gingivalis at 95% probability. J Periodontal 1992; 63:418–125.