510 ORDER IV. EUBACTERIALES 



important characters of a species. Before the identify of a Streptococcus culture should be 

 regarded as established, the complete physiological pattern should be determined and com- 

 pared with the complete physiological patterns of the species in the genus. 



Key to the species of genus Streptococcus. 



The Pyogenic Group 



I. No growth at 10° or 45° C. (some exceptions in Streptococcus sanguis). No growth in 

 6.5 per cent NaCl broth, at pH 9.6 or in 0.1 per cent methylene blue milk. No reduction 

 of litmus before curdling milk. Tyrosine not decarboxylated. 



A. Sodium hippurate not hydrolyzed. 



1. High COo tension not required for rapid growth on blood agar. Cells and colonies 

 not "minute." Ammonia produced from arginine. 



a. No viscous polysaccharide produced in 5 per cent sucrose broth. Inulin not 

 fermented, 

 b. Fibrinolytic. 



0. Beta hemolytic. Ferments trehalose but not sorbitol, 

 d. Glycerol not fermented. Lancefield group A. 



1. Streptococcus pyogenes. 



dd. Glycerol fermented aerobically. Lancefield group C. 



2. Streptococcus equisimilis. 

 bb. Not fibrinolytic. 



c. Beta hemolytic. 



d. Trehalose not fermented, but sorbitol fermented. Glycerol 

 fermented aerobically. Lancefield group C. 



3. Streptococcus zooepidemicus . 



dd. Trehalose, sorbitol and glycerol not fermented. Lancefield group 

 C. 



4. Streptococcus egui. 



cc. Not beta hemolytic. Trehalose fermented. Sorbitol usually fer- 

 mented. Glycerol not fermented. Lancefield group C. 



5. Streptococcus dysgalactiae. 



aa. Viscous polysaccharide produced in 5 per cent sucrose broth. Inulin usually 

 fermented. May or may not be beta hemolytic. Lancefield group H. 



6. Streptococcus sanguis.* 



2. High CO2 tension required for rapid growth on blood agar. "Minute" cells and 

 colonies. Ammonia produced from arginine. Lancefield group F and Type I, 

 group G. 



7. Streptococcus anginosus. 



B. Sodium hippurate hydrolyzed. 



1. Ammonia produced from arginine. Glycerol fermented aerobically. May be beta 

 hemolytic. Final pH in glucose broth, 4.2 to 4.8. Lancefield group B. 



8. Streptococcus agalactiae. 



The Viridans Group 



2. Ammonia not produced from arginine. Glycerol not fermented. Not hemolytic. 

 Final pH in glucose broth, 5.6 to 6.5. 



9. Streptococcus acidominimus . 



II. No growth at 10° C. Growth at 45° C. (exceptions in Streptococcus mitis). No ammonia 



* Although no group antigen has been demonstrated for Streptococcus sanguis, this 

 species and the group H streptococci are similar enough in other characteristics to warrant 

 their association. See detailed description of this species. 



