What does gamma-hemolysis indicate on blood agar?

What does gamma-hemolysis indicate on blood agar?

• A. Partial hemolysis with green halo
• B. No hemolysis around colonies
• C. Complete hemolysis with a clear zone
• D. Growth inhibition around colonies

Answer: (B)

On blood agar, bacteria are evaluated by how they affect surrounding red blood cells. Gamma-hemolysis means there is no lysis of red blood cells under the tested conditions. The medium around the colonies stays the same color, with no clearing or color change, even though the bacteria may grow. This non-hemolytic pattern is what “gamma” denotes. In contrast, alpha-hemolysis shows a partial lysis with a greenish halo due to partial breakdown of hemoglobin, while beta-hemolysis shows a clear zone from complete lysis of red blood cells.

On blood agar, bacteria are evaluated by how they affect surrounding red blood cells. Gamma-hemolysis means there is no lysis of red blood cells under the tested conditions. The medium around the colonies stays the same color, with no clearing or color change, even though the bacteria may grow. This non-hemolytic pattern is what “gamma” denotes.

In contrast, alpha-hemolysis shows a partial lysis with a greenish halo due to partial breakdown of hemoglobin, while beta-hemolysis shows a clear zone from complete lysis of red blood cells.