CHARACTERIZATION OF PREVOTELLA-INTERMEDIA AND PREVOTELLA-NIGRESCENS ISOLATES FROM PERIODONTIC AND ENDODONTIC INFECTIONS

THE OCCURRENCE AND SURFACE PROPERTIES Of Prevotella intermedia and P. nigrescens in healthy sites and in periodontic and endodontic infectio ns were studied among 73 strains, tentatively identified as P. interme dia. Fifteen strains were from necrotic root canal infections, 41 were from periodontal samples, and 17 isolates were obtained from healthy gingival sites. Identification of isolates as either P. intermedia or P. nigrescens was based on differences in malate and glutamate dehydro genase electrophoretic mobilities which allowed unambiguous separation of P. intermedia and P. nigrescens. The majority of strains from peri odontal samples were P. intermedia (29 of 41 strains). In endodontic s amples only 4 out of 15 isolates were P. intermedia, while all except 1 of 17 strains from healthy gingival sites were identified as P. nigr escens. SDS-PAGE of whole cell proteins revealed 31 and 38 kDa protein s in P. nigrescens which were not detected in P. intermedia. Surface b iotinylation of cells, followed by Western blotting and detection by a lkaline phosphatase conjugated extravidin, showed strong staining of t he 31 kDa protein in P. nigrescens indicating that this protein is loc ated on the surface of the cell. Corresponding staining was not seen i n P. intermedia. Fimbria-like projections were observed using electron microscopy of negatively-stained cells of P. nigrescens. The results show that P. intermedia and P. nigrescens may have different site spec ificities and surface properties and thus emphasize the need for accur ate identification of these two species for the evaluation of their ro le in the pathogenesis of oral infections.