OPTIMIZED OLIGONUCLEOTIDES FOR THE DIFFERENTIATION OF PREVOTELLA-INTERMEDIA AND PREVOTELLA-NIGRESCENS

The gram-negative, anaerobic bacterium Prevotella intermedia plays an important role in the progression of periodontitis, whereas the etiolo gical role of the closely related but phenotypically indistinguishable species Prevotella nigrescens is controversial. To differentiate betw een these species properly, 16S rDNA/RNA directed, computer-optimized oligonucleotides were designed and tested with 26 P. intermedia, 26 P. nigrescens and a number of closely and more distantly related strains . The oligonucleotides were used as primers in a polymerase chain reac tion and could be demonstrated to be species specific with a detection limit of 50 bacterial cells, which could also be detected when dilute d 1:10(5) with different plaque bacteria. In addition, the described o ligonucleotides were digoxigenin-labeled at the 3' end and used as DNA probes in a dot blot hybridization assay. This assay, although slight ly less sensitive than the polymerase chain reaction-based method, gav e species-specific reactions and also allowed (semi-)quantification of bacterial cells in clinical specimens.