Interactions of Bacteroides gingivalis with fibrinogen.

Results of previous studies from our laboratory have shown that a strain of Bacteroides intermedius isolated originally from a patient with acute necrotizing ulcerative gingivitis binds and degrades human fibrinogen (M.S. Lantz, L.M. Switalski, K.S. Kornman, and M. Hook, J. Bacteriol. 163:623-628, 1985). We report that strains of Bacteroides gingivalis, an organism implicated in the etiology of several forms of periodontitis, also bind and degrade fibrinogen. The binding is rapid, reversible, saturable, and specific. The number of fibrinogen-binding sites per cell varies from 500 to 1,500 in different batches of bacteria, and the dissociation constant for the complex is on the order of 10(-8) M. B. gingivalis possesses cell-associated fibrinogenolytic activity that is activated by dithiothreitol and blocked by thiol protease inhibitors. Interaction with fibrinogen may mediate colonization and establishment of these organisms in the periodontal microbiota.