This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology Pa 1 (Gram Positive Cocci, Gram Negative Cocci), Subject name: Microbiology
Which toxin of streptococcus causes hemolysis around colonies: 
Select and explain. 
A. Streptolysin O, B. Streptolysin S, C. Streptodornanse, D. Hyaluronidase
B: Streptolysin S
Answer: B: Streptolysin S 
Explanation: Option 1, 2 Streptolysin 'O' Streptolysin 'S' Oxygen labile Oxygen stable Hemolysis in reduced state only Hemolysis around streptococcal colonies. Cannot cause hemolysis on the surface of blood agar. Option 3 DNase/ Deoxyribonuclease/Streptodornanse : Diagnostic use: Anti-DNase B > 300-350 U is useful for the retrospective diagnosis of skin infections (pyoderma) and acute glomerulonephritis where ASO titer is low. Option 4 Hyaluronidase (spreading factor): Expressed by non-capsulated strains, such as M type 4 and 22.