Binding of plasminogen to Pseudomonas aeruginosa results in formation of surface-associated plasmin and enhanced bacterial invasiveness.

The interaction of Pseudomonas aeruginosa with plasminogen (Plg) is herein reported. Plg bound similarly to laboratory and clinical P. aeruginosa isolates from blood of septicemic patients and stools of asymptomatic carriers. No difference in Plg capture was detected between the piliated PAK strain and its isogenic nonpiliated mutant. Western immunoblotting results suggested that low molecular weight nonpilus adhesins from the bacterial outer membranes accounted for the Plg capture. Bacteria-bound Plg was converted to bioactive plasmin in the presence of exogenous urokinase-type Plg activator. The presence of surface-bound plasmin enhanced significantly the P. aeruginosa capability to invade fibrin gels and a reconstituted basement membrane matrix. These findings support the concept that Plg capture by P. aeruginosa may represent a mechanism which offers advantages to bacterial invasiveness through tissue barriers.