Persistence patterns of Porphyromonas gingivalis, Prevotella intermedia/nigrescens, and Actinobacillus actinomycetemcomitans after mechanical therapyof periodontal disease

Background: The aim of this study was to determine the distribution pattern s of Porphyromonas gingivalis, Prevotella intermedia/nigrescens, and Actino bacillus actinomycetemcomitans in periodontitis patients after standard mec hanical periodontal therapy, and to determine factors increasing the odds t o detect these target organisms in treated sites. Methods: Eight hundred fifty-two (852) separate subgingival microbial sampl es were taken from the mesial and distal aspects of every tooth in 17 patie nts. Target organisms were identified culturally. Results: The 3 microorganisms showed different persistence patterns: P. gin givalis was detected in a high percentage of subjects (59%), but in a low p roportion of sites (5.4%). P. intermedia/nigrescens was detected in all sub jects except one, and in 40.6% of the tested sites. Only 5 subjects were A. actinomycetemcomitans positive, but 2 of them showed a very high number of positive sites (44% and 75%, respectively). A highly significant relations hip was found between a subject's tendency to bleed upon sampling and the n umber of P. intermedia/nigrescens-positive sites. A significant portion of the variation in frequency of persisting P. gingivalis could be explained b y the frequency of persisting pockets deeper than 4 mm. No similar relation ship could be established between clinical parameters and A. actinomycetemc omitans. On a site level, the odds of detecting P. gingivalis increased by a factor of 2.47 (P = 0.0001) for every millimeter of residual probing dept h; the odds of detecting P. intermedia/nigrescens increased by a factor of 1.84 (P = 0.0001). Conclusions: If, after standard mechanical periodontal therapy, a large num ber of sites continue to bleed, one may expect an increased number of sites positive for P. intermedia/nigrescens. If many deep pockets persist, a gre ater number of P. gingivalis-positive sites can be expected.