Hemolysin test procedure

The hemolysin test is used to check if bacteria can produce hemolysins. (It is a substances that break down red blood cells (RBCs). By breaking RBCs, hemolysins release hemoglobin, which is visible on special plates called blood agar plates.

Here is the Hemolysin test procedure steps.

1. Blood agar is made by mixing a nutrient-rich agar with 5% defibrinated sheep or horse blood.
2. Using a sterile tool, spread the bacterial sample onto the surface of the blood agar plate.
   • You can test multiple bacteria on one plate by streaking method.
3. Place the plate in an incubator at 35-37°C for 18-24 hours. Some bacteria might need low-oxygen conditions to grow properly.
4. After incubation, look for color changes or clear zones around the bacteria to determine what type of hemolysis has occurred.

What are the types of hemolysis?

1. Alpha (α) Hemolysis:

• The bacteria only partially destroy RBCs.
• This results in a greenish or brown area around the colonies.
• Example: Streptococcus pneumoniae.

1. Beta (β) Hemolysis:

• The bacteria completely destroy RBCs.
• This creates a clear zone around the colonies where all the blood cells have been destroyed.
• Example: Streptococcus pyogenes.

1. Gamma (γ) Hemolysis:

• No RBC destruction occurs.
• The blood agar remains unchanged, with no clear or discolored zones around the colonies.
• Example: Enterococcus faecalis.

How to read the hemolysin test?

• Beta hemolysis indicates the bacteria are aggressive and can destroy RBCs completely.
• Alpha hemolysis shows partial RBC destruction, which often occurs with bacteria that are less harmful.
• Gamma hemolysis means no RBCs are broken down, which typically points to a non-harmful bacterial strain.