Question

Which hemolysis test (alpha beta gamma) is S. aureus positive for?

1) Alpha
2) Beta
3) Gamma

Answer 1

Staphylococcus aureus is positive for beta-hemolysis, which is indicated by a clear zone surrounding the colonies on blood agar plates. It can also be distinguished from other staphylococci by its positive coagulase test and its ability to ferment mannitol.

Step-by-step explanation:

Staphylococcus aureus is positive for beta-hemolysis. Beta-hemolysis is a complete lysis of red blood cells and is evident by a clear zone surrounding the colonies on blood agar plates. This is in contrast to alpha-hemolysis, which is a partial hemolysis causing a greenish hue around the colonies, and gamma-hemolysis (y-hemolysis), which results in no hemolysis and no change in the appearance of the agar around the colonies.

S. aureus can also be identified by its positive coagulase test, which differentiates it from other staphylococci. The enzyme coagulase is associated with the pathogenicity of S. aureus, and this characteristic, combined with its ability to cause beta-hemolysis and ferment mannitol, can help confirm its presence in laboratory cultures.

Answer 2

S. aureus is beta-hemolytic, which is confirmed by a clear zone around the colonies on blood agar. It produces the enzyme coagulase, distinguishing it from other staphylococci. Therefore, the correct answer is 2.

Step-by-step explanation:

​Staphylococcus aureus (S. aureus) is known to be beta-hemolytic (option 2) when grown on blood agar plates. This means that it produces a clear zone around the colonies due to the complete lysis of red blood cells. The enzyme coagulase, which S. aureus produces, is a distinguishing factor from other species of staphylococci and is used alongside other tests like the Gram stain and catalase test for confirmation in clinical laboratories. Conversely, alpha hemolysis represents partial lysis that results in a greenish color around the colonies, and gamma hemolysis is indicated by no change in the agar surrounding the bacteria.