Direct detection of Prevotella intermedia and P. nigrescens in suppurative oral infection by amplification of 16S rRNA gene.

A specific 16S rDNA PCR and subsequent hybridisation reaction was designed to discriminate between strains of Prevotella intermedia (n = 15) and P. nigrescens (n = 15). This technique was then used to detect the presence of these two bacterial species in acute suppurative oral infection. A total of 36 pus samples aspirated from 26 peri-apical abscesses, three root canals, three periodontal abscesses, two cases of refractory periodontitis, one cyst and one haematoma was examined. A portion of the pus sample was processed by PCR and the remainder of the specimen was subjected to routine culture. The PCR-based technique gave an identical pattern of detection of P. intermedia or P. nigrescens to that obtained by culture for 30 of the 36 specimens. Either P. intermedia or P. nigrescens was present in 14 samples and neither species was detected in 16 samples. In the remaining six samples the PCR method indicated the presence of one (n = 3) or both (n = 3) of the Prevotella species but neither or only one species was isolated by culture. It is concluded that the presence of P. intermedia and P. nigrescens in pus can be detected rapidly and specifically by direct PCR amplification of 16S rDNA. P. nigrescens was detected more frequently than P. intermedia in suppurative peri-apical infection both by culture and PCR.