The Differentiation of Hemolytic Streptococci from Various Sources by the Group Precipitin Reaction and by Biochemical Tests

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Abstract
Among 241 cultures of hemolytic streptococci from human sources, 156 fell in serologic Group A, 13 in Group B, 9 in Group C, 6 in Group D, 1 in Group F, 28 in Group G, 3 in Group H, and 25 failed to react. Of 188 strains associated with infections 142 were Group A. Among 320 cultures from animal sources, chiefly from milk, 12 fell in Group A, 263 in Group B, 15 in Group C, 2 in Group D, 4 in Group E, 10 in Group G, 1 in Group H, and 13 failed to react. Tests for fermentation of sorbitol, trehalose, salicin and lactose were of value in differentiation of vars. within the serologic groups. Tests for fermentation of glycerol and mannitol, curdling of milk, hydrolysis of starch and production of soluble hemolysin were of limited differential value. Double zones of hemolysis in rabbit blood plates were formed by about half the Group B cultures but not by cultures of other groups. The sodium hippurate test was a reliable means of identifying Group G strains. The group precipitin reaction using either Lancefield''s macroscopic technic or Brown''s microscopic method is a simple and accurate means of identifying hemolytic streptococci.

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