Dairy Microbiology

Types of hemolysis
Alpha , Beta and gamma hemolysis 📍

🔴 Hemolysis is the break down of the membrane of red blood cells by a bacterial protein known as hemolysin, which causes the release of hemoglobin from the red blood cell.

🔴 There are three types of hemolysis designated : alpha, beta and gamma.

🔼 Alpha hemolysis/ is a greenish discoloration that surrounds a bacterial colony growing on the agar.
This type of hemolysis represents a partial decomposition of the hemoglobin of the red blood cells. Alpha hemolysis is characteristic of Streptococcus pneumonia and so can be used as a diagnostic feature in the identification of the bacterial strain.

🔼 Beta hemolysis/ represents a complete breakdown of the hemoglobin of the red blood cells in the vicinity of a bacterial colony. There is a clearing of the agar around a colony. Beta hemolysis is characteristic of Streptococcus pyogenes and some strains of Staphylococcus aureus.

🔼 This type of hemolysis is actually no hemolysis at all. Gamma hemolysis is a lack of hemolysis in the area around a bacterial colony. A blood agar plate displaying gamma hemolysis actually appears brownish. This is a normal reaction of the blood to the growth conditions used (37° C in the presence of carbon dioxide). Gamma hemolysis is a characteristic of Enterococcus faecalis.

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