ACTIVATION OF BLOOD-CLOTTING FACTORS BY MICROBIAL PROTEINASES

There are very few reports on the involvement of bacterial proteinases on the blood clotting system using both human plasma and purified clo tting factors. We studied whether microbial proteinases from the oppor tunistic pathogens Candida albicans, Pseudomonas aeruginosa and Serrat ia marcescens activate the blood clotting cascade by using normal huma n plasma, human plasmas deficient in clotting factor XII or X, and als o by using purified clotting factors XII, X and prothrombin. All prote inases tested activated either clotting factor XII or prothrombin in v itro, thus resulting in generation of thrombin. Clotting factor X was converted to the active form (Xa) by both Candida and Pseudomonas prot einases, but not by Serratia proteinase. These results suggest that pe ripheral and systemic blood circulation may be impaired by activation of the blood clotting cascade by microbial infections, especially in s eptic patients, which would enhance disseminated intravascular coagula tion and multi-organ failure.