Effect of Dissociation of Streptococci on their Fibrinolytic And Anticlotting Activity

Abstract

Tillett and Garner1 made the interesting observation that broth cultures of beta hemolytic streptococci of human origin rapidly dissolve the normal human fibrin clot and that the dissolving action is dependent upon an extracellular substance. With the exception of some strains of Staphylococcus aureus, fibrinolysis appears to be peculiar to the hemolytic streptococcus and it has not been demonstrated with other bacteria including Streptococcus viridans, pneumococcus and most strains of hemolytic streptococci of animal origin. Hadfield, Magee and Perry2 found a greater variation in the dissolving power of their strains of hemolytic streptococci than described by others. They observed that the strains of hemolytic streptococci which were virulent for mice and formed colonies corresponding to the colonies called smooth in this country, were the strongest fibrinolytic strains. As their strains became less virulent they became less fibrinolytic. For my tests streptococci were grown 20 hours in meat extract 1 per cent dextrose broth, pH 7.0. If they would not grow in this medium one drop of defibrinated sheep blood was added to 5 cc. of dextrose broth. In general the method of Tillett and Garner was followed. As it is more convenient to use small amounts of blood, it is collected from the finger or ear into bent capillary pipets containing 2 per cent sodium citrate in salt solution. Two-tenths per cent potassium oxalate give the same results. Two parts of blood are drawn into a pipet containing one part of the anticoagulant and diluted at once with eight parts of physiological salt solution and centrifuged. The plasma is used within one hour after the blood has been collected, although it may be kept 24 hours in the ice box before using. Four parts of the diluted plasma are mixed with two parts of broth culture and one part of 0.25 per cent CaCl2 in small test tubes. The mixtures are incubated at 36-37 C. The control containing plasma, uninoculated broth and CaCU clots in from 5-15 minutes. When broth cultures of hemolytic streptococci dissolve the plasma clot, it occurs in from 15 minutes to 24 hours after its coagulation. Nineteen strains of hemolytic streptococci, from scarlet fever (8), erysipelas (6, including the pigmented yellow dissociant), septic sore throat (2),