ANALYSIS OF PLASMIN(OGEN) ACQUISITION BY CLINICAL ISOLATES OF GROUP-ASTREPTOCOCCI INCUBATED IN HUMAN PLASMA

Group A streptococci isolated from throat swabs or blood cultures were compared for the expression of plasmin(ogen) receptors. The majority of isolates bound I-125-labeled Lys-plasmin and I-125-labeled Lys-plas minogen while displaying minimal reactivity with I-125-labeled Glu-pla sminogen. All streptococcal isolates could acquire surface enzymatic a ctivity when incubated in human plasma but not if the plasma had been depleted of plasminogen. The ability to acquire surface enzymatic acti vity was limited by the quantity of streptokinase in the reaction mixt ure. There was no statistically significant difference between group A streptococci isolated from throat swabs and those from blood cultures with respect to their interaction with components of the fibrinolytic system in human plasma. However, these isolates could be divided into two groups based on their ability to acquire surface enzymatic activi ty when incubated in plasma with exogenous streptokinase. Surprisingly , the acquisition of surface enzymatic activity when incubated in plas ma containing streptokinase was not always correlated with the plasmin (ogen) binding capacity determined by direct binding of radiolabeled l igands. Analysis of this phenomenon suggests that group A streptococci can use diverse mechanisms to acquire plasmin(ogen)-dependent enzymat ic activity.