MICROBIAL ASSOCIATIONS OF 4 PUTATIVE PERIODONTAL PATHOGENS IN SUDANESE ADULT PERIODONTITIS PATIENTS DETERMINED BY DNA-PROBE ANALYSIS

THE FEW PREVIOUS CULTIVATION STUDIES on the in vivo associations between various periodontal microbial species have shown several positive and negative associations. The present investigation utilized DNA probe analysis to examine possible in vivo associations between the periodontal pathogens Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Bacteroides forsythus in subgingival plaque samples obtained from 25 Sudanese untreated adult periodontitis patients. The standard paper point technique was used to sample 99 sites with a mean probing depth of 6.8 mm (range 6.0 to 10.0). Microbial associations were determined by detecting the effect of the presence or absence of one species (effector) on the occurrence of the other 3 species (target). The Wilcoxon signed rank test was used to examine variations in occurrence of each target bacteria in the presence or absence of the effector. In addition, the Spearman's rank correlation test was used to assess the relationship between the level of each bacteria to that of the other 3. Results showed bacterial associations with the following effector-on-target effects: F. nucleatum (P < 0.01 Wilcoxon; P < 0.001 Spearman) >> P. gingivalis (P < 0.01 Wilcoxon; P < 0.001 Spearman), and B. forsythus (P < 0.05 Wilcoxon; P < 0.001 Spearman) > P. intermedia (P < 0.01 Spearman). The study demonstrated positive associations between the 4 species investigated, while no neutral or negative associations were revealed. The most striking finding was the effect exerted by F. nucleatum on the colonization of P. intermedia; P. intermedia was never detected in a site unless F. nucleatum was also present.