Effect of Varidase (streptokinase) on biofilm formed by Staphylococcus aureus

Staphylococcus aureus forms a fibrin-rich biofilm in the presence of plasma which is highly resistant to attack by the human immune system and to chemotherapy. Varidase, composed mainly of streptokinase, is used for hydrolyzing clots. In this study, we attempted to destroy the biofilm of S. aureus with Varidase and to apply this drug in the treatment of staphylococcal infections. Four clinical isolates were used in the experiments. These organisms formed a several-millimeter-thick biofilm on type IV collagen coated coverslips in trypticase soy broth containing 50% human plasma. The biofilm was composed of bacterial cell which adhered to fibrillar fibers and of sediment derived from plasma. 10,000 U/ml of Varidase, the dose which is used clinically, removed the sediment and reduced the number of live bacteria in biofilms to less than 20% of control. 200 U/ml of Varidase was also effective against biofilms of the organisms. An equal combination of Varidase and ofloxacin had an additive effect on the bacteria. The results of this study demonstrate that Varidase is highly effective in destroying biofilms of S. aureus in vitro and suggest that this drug would be useful for treating staphylococcal infections.