On blood agar plates, a small zone of alpha hemolysis surrounded by a zone of beta hemolysis is known as what type of hemolysis?

The small zone of alpha hemolysis surrounded by a zone of beta hemolysis is classified as alpha-prime hemolysis. This phenomenon occurs when certain bacteria, typically streptococci, produce alpha hemolysin that exhibits incomplete lysis of red blood cells in a narrow margin around the growth, while the surrounding area shows complete lysis due to the action of beta hemolysins produced by the same or adjacent bacteria. The combination creates a distinct appearance on blood agar plates, which is recognized in microbiological identification.

In contrast, beta hemolysis refers to complete lysis of red blood cells, resulting in a clear zone around the colony, while alpha hemolysis demonstrates partial lysis, presenting as a greenish discoloration. Gamma hemolysis indicates no lysis at all. Understanding these different types of hemolysis is crucial for identifying and differentiating bacterial species based on their hemolytic patterns on blood agar.