Role of Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens in extraoral and some odontogenic infections.

Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens were isolated from 138 subjects with various infections (intraabdominal, skin and soft-tissue, head and neck, pleuropulmonary, and odontogenic infections and bacteremia). The phenotypic identification of 173 isolates was completed by molecular methods. Arbitrarily primed polymerase chain reaction (AP PCR) analysis was used to determine the genetic similarity of intraindividual P. intermedia/P. nigrescens group isolates recovered from 12 subjects. All 19 P. gingivalis isolates (16 intraabdominal isolates and three odontogenic isolates) hybridized with the P. gingivalis-specific DNA probe. Of the 154 P. intermedia/ P. nigrescens group isolates, 74 were identified as P. intermedia; 78, as P. nigrescens; and 2, as P intermedia/P. nigrescens-like isolates. P. intermedia and P. nigrescens were isolated with equal frequency from patients with all other infections except those with bacteremia, from whom only P. nigrescens isolates were recovered. There were 12 cases in which multiple P. intermedia/ P. nigrescens group isolates were recovered; in nine, only one of the species was isolated, whereas in three, two different species were detected. The intraindividual isolates representing the same species always exhibited identical AP PCR genotypes.