Further studies on some physical and biochemical characteristics of asaccharolytic pigmented Bacteroides of feline origin.

The ultrastructure of the appendages of 24 strains of asaccharolytic pigmented Bacteroides spp. of cats was studied by transmission electron microscopy. All strains examined by thin section showed abundant fimbriae, outer membrane vesicles and capsules. Negative staining showed fimbriae which varied from long, fine and wavy in Bact. salivosus and cat Group 2 to shorter, less abundant and thicker fimbriae in cat strains of Bact. gingivalis as well as type strains of Porphyromonas gingivalis and P. asaccharolytica. Capsular material was very thick amorphous in human P. gingivalis, cat strains of Bact. gingivalis and in P. assaccharolytica but fine and fibrillary in preparations of Bact. salivosus and cat Group 2 organisms. Wet india ink preparations showed a large capsule although those of Bact. salivosus and Group 2 appeared largest. Five-day Group 2 broth cultures featured a thick ropy growth consistent with a large accumulation of extracellular slime. Enzymatic activities of the 24 strains measured by API ZYM system as well as the conventional biochemical tests showed it was possible to differentiate reliably Bact. salivosus from the other cat strains of asaccharolytic pigmented Bacteroides species and from human P. gingivalis and P. endodontalis by a combination of these tests. These tests suggest that Bact. salivosus is unlikely to belong to the genus Prevotella. Its place within the genus Porphyromonas is still to be determined.