Association of black-pigmented bacteria with endodontic infections

Black-pigmented bacteria (BPB) have been associated with endodontic infecti ons, The purpose of this study was to evaluate further the presence of BPB with the clinical signs and symptoms associated with endodontic infections. Microbial samples were collected from the root canals of 40 intact teeth w ith necrotic pulps and apical periodontitis. Conventional laboratory method s were used for identification of the strains of BPB isolated in pure cultu re, In addition, the polymerase chain reaction and specific primers for 16S r-RNA genes were used to differentiate Puevotella nigrescens from Puevotel la intermedia. Twenty-two (55%) samples were positive for the growth of BPB , Of those, 11 of 22 (50%) were identified as P. nigrescens, 8 of 22 (36%) were P. intermedia, 2 of 22 (9%) were Porphyromonas gingivalis, and 1 of 22 (5%) was Prevotella melaninogenica, Sixteen of the 22 root canals positive for the growth of BPB were associated with purulent drainage either from t he root canal or an associated sinus tract. Statistical analysis did not sh ow a significant relationship for the presence of BPB with clinical signs a nd symptoms.