Bacteroides intermedius binds fibrinogen

The binding of Bacteroides intermedius VPI 8944 to human fibrinogen has been characterized. The binding is time dependent, at least partially reversible, saturable, and specific. On an average, a maximum of 3,500 fibrinogen molecules bind per bacterial cell, with a dissociation constant of 1.7 x 10^-11 M. These bacteria also exhibit a fibrinogenolytic activity which can be partially inhibited by protease inhibitors. Bacteria release fibrinogenolytic activity into the surrounding medium without loss of binding activity, but more pronounced fibrinogen breakdown occurs when ¹²⁵I-labeled fibrinogen is associated with the bacteria, suggesting that fibrinogen is degraded at the cell surface. Fibrinogen binding by B. intermedius might represent a mechanism of bacterial tissue adherence.