Binding of fibrinogen degradation products to S. aureus and to beta-hemolytic streptococci group A, C and G.

Binding of fibrinogen degradation products was measured to Gram-positive cocci known to carry receptors for human fibrinogen. Forty-one strains of S. aureus and group A, C and G streptococci were studied. The largest plasmin produced fragment (X-fragment, HMWDP) showed higher binding levels to the bacterial receptors in all four species as compared to intact fibrinogens. The enzymatically produced C-terminal fragment D was strongly reactive, whereas the N-terminal fragment E was non-reactive. Inhibition experiments showed that reactive fragments were bound to the same receptors as fibrinogen. Three chemically-produced and well-characterized fragments from the terminal and the middle portions of the fibrinogen molecule were all negative in binding assays. The binding patterns for fibrinogen and the fragments tested were identical in the four bacterial species tested, S. aureus and group A, C and G streptococci. The results confirm and extend earlier data on similarities between fibrinogen receptors on these Gram-positive bacterial species.