Identical clonal types of Porphyromonas gingivalis or Prevotella nigrescens recovered from infected root canals and subgingival plaque.

Clinical samples from 10 infected root canals and from subgingival plaque in 10 patients were screened by anaerobic culture for black-pigmented anaerobes. A total of 17 Porphyromonas gingivalis and 9 Prevotella nigrescens were obtained from four patients and were identified by species-specific polymerase chain reaction (PCR) amplification. The arbitrarily primed PCR reaction used to examine the genetic diversity of the isolates revealed that the P. gingivalis or P. nigrescens simultaneously present in the root canal system and in subgingival plaque of all four patients were genotypically indistinguishable. These data indicate that the endodontium and the periodontium can be colonized by the same clonal types of black-pigmented anaerobes.