Phenotypic characterization of human and animal biotypes within the species Porphyromonas gingivalis

Ninety-nine strains of Gram-negative black-pigmented anaerobic rods, grown on Todd-Hewitt blood agar plates, were identified and characterized according to a typing scheme including UV fluorescence, catalase, trypsin-like and haemagglutinating activities, biochemical tests with the ATB 32A kit, and gas-liquid chromatography. To determine the taxonomic position of the Porphyromonas gingivalis biotypes, 68 strains (31 of human origin and 37 of animal origin) were compared to 31 strains of closely related species or of uncertain generic status. Most animal strains were isolated in our laboratory by subculturing samples from the oral cavity of five mammalian species (bear, cat, coyote, dog and wolf). Those strains differed from human P. gingivalis strains in that they were positive for catalase, beta-galactosidase and glutamyl-glutamic acid arylamidase; from Bacteroides macacae by more rapid pigmentation, positive haemagglutination, failure to produce propionic acid, and negative alpha-galactosidase; and from Bacteroides salivosus by more rapid pigmentation, positive haemagglutination and failure to produce propionic acid. These data demonstrate that phenotypic heterogeneity within the taxon P. gingivalis can be resolved into two biotypes, each corresponding to a human source or an animal source.