The role of streptococcal plasmin(ogen) binding in infective endocarditis

The ability of viridans group streptococci (VGS) to bind human plasminogen and its subsequent activation into plasmin may contribute to the pathogenesis of streptococcal endocarditis. The increased proteolytic activity acquired through cell-bound plasmin may lead to a decreased stability of the streptococcal vegetation and possible embolisation. Twenty-two infective endocarditis isolates and 16 non-infective endocarditis isolates were screened for their ability to bind plasminogen through the quantification of its active form plasmin, using the colorimetric substrate D-Val-Leu-Lys p-nitroanilide. The species of the VGS assessed expressed a universal capability to bind human plasminogen, although they did so with differing affinities and independently of the site of isolation.