Surface bound plasmin promotes migration of Streptococcus pneumoniae through reconstituted basement membranes

Penetration of basement membrane is believed to be an essential step in the pathogenesis of bacterial meningitis. Consequently Streptococcus pneumonia e strains were tested for their ability to adhere to reconstituted basement membrane (Matrigel) and in a proceeding step penetrate this membrane by th e use of surface activated plasmin. A majority of S. pneumoniae strains tes ted were found to adhere to reconstituted basement membrane as well as to t he purified laminin component. Three out of seventeen strains also adhered to the collagen IV component. All the investigated strains also demonstrate d a capacity to bind plasminogen with up to 42,000 plasminogen binding site s per bacterium as estimated by Scatchard analysis. Two strains selected fo r optimal adhesion and plasminogen binding were further tested for basement membrane penetration using a dual chamber model. Our data show that penetr ation was achieved within 3-4 h in the presence of plasminogen whereas with out plasminogen no strain was able to penetrate during a 21 h incubation. T he results suggest a potential role of surface associated plasminogen in ba cterial penetration of basement membranes and extracellular matrix. (C) 199 9 Academic Press.