Interaction of a group A Streptococcus within human plasma results in assembly of a surface plasminogen activator that contributes to occupancy of surface plasmin-binding structures

Group A streptococcal isolate 187061 incubated in human plasma or serum reconstituted with fibrinogen but not plasminogen-depleted plasma or serum alone acquired a surface plasminogen activator activity. Assembly of the surface plasminogen activator was inhibited by the presence of neutralizing antibodies to streptokinase. Once assembled, the bacterial-associated plasminogen activator could generate plasmin when incubated in human plasminogen, plasmin or serum which could bind to bacterial surface plasmin-binding structures despite the presence of host physiological inhibitors. These studies provide evidence that the pathways by which group A isolates interact with human plasmin(ogen) are potentially linked and may provide a mechanism for bacteria to acquire host enzymatic activity efficiently in the infected host.