Interaction between group A streptococci and the plasmin(ogen) system promotes virulence in a mouse skin infection model

Group A streptococci are capable of acquiring a surface-associated, unregul atable plasmin-like enzymatic activity when incubated in human plasma. The effect of this enzymatic activity on virulence of group A isolate CS101 was examined in a mouse skin infection model. Initial studies demonstrated enh anced virulence for bacteria preincubated in human plasma but not in plasmi nogen-depleted plasma. A direct correlation between surface-associated enzy matic activity and virulence was not observed; however, an association betw een virulence and the assembly of a surface-associated plasminogen activato r that could activate mouse plasminogen was noted. This activity enhanced v irulence in wild type but not in plg(-/-) plasminogen-deficient mice, These results support the hypothesis that acquisition of a surface-associated pl asmin(ogen)-dependent enzymatic activity can contribute to the virulence of group A streptococcal invasive infections.