OCCURRENCE OF PREVOTELLA-NIGRESCENS AND PREVOTELLA-INTERMEDIA IN INFECTIONS OF ENDODONTIC ORIGIN

The occurrence of Prevotella intermedia and Prevotella nigrescens in e ndodontic infections was studied using sodium dodecyl sulfate polyacry lamide gel electrophoresis (SDS-PAGE) of whole cell protein to disting uish between the species. Previous studies have shown an association b etween black-pigmented bacteria (BPB) and endodontic infections and th at Prevotella intermedia (previously known as Bacteroides intermedius) was the most commonly isolated BPB. Recently, however, strains identi fied as P. intermedia were shown to in fact be composed of two separat e species, P. intermedia and P. nigrescens. Fifty-six strains of BPB i solated from endodontic infections and previously identified as P. int ermedia were used in this study. Following SDS-PAGE, P. nigrescens sho wed a unique 18.6 kDa band that was used to differentiate P. nigrescen s from P. intermedia. Of the 56 strains of BPB, 41 (73.2%) were identi fied as P. nigrescens and 15 (26.8%) as P. intermedia. This study conf irms that P. nigrescens, and not P. intermedia, is the BPB most often isolated from infections of endodontic origin.