In vitro attachment, salivary agglutination, and surface fibril density of fresh Actinomyces isolates from two distinct oral surfaces.

Whereas attachment specificity among bacterial species is well recognized, the question of specificity among strains of the same species isolated from distinct oral surfaces has not been studied. Twenty strains of Actinomyces, freshly isolated as they re-populated the cleaned teeth and tongues of a male twin pair, were compared for: (1) their ability to attach to saliva-coated hydroxyapatite (SHA), (2) the density of their surface fibrils, (3) their agglutination in saliva, and (4) their ability to agglutinate human erythrocytes. Differences among the strains were mostly along species rather than tissue source lines. The A. naeslundii strains were the least efficient in SHA attachment and had the least number of fibrils, but they were the most strongly agglutinated strains in saliva. The A. viscosus strains, while showing some tissue source differences in hemagglutination, were consistently alike in SHA attachment and fibril density. Salivary agglutination did not correspond with the ability to attach to SHA. Considering the surface characteristics of the Actinomyces species studied, strains of the same species isolated from distinct oral surfaces are apparently more alike than strains of the two closely-related species isolated from the same surface.