Medical Microbiology Quizzes: Blood Agar Differential Media

Which type of hemolysis results in a clearing of the blood agar?

What is the primary advantage for organisms that are able to produce hemolysins?

Which statement is true about α-hemolysis in the context of blood agar?

What is the primary target of hemolysins produced by certain Gram-positive cocci?

What can you observe when viewing a plate with -hemolytic organisms held up to the light?

Why are organisms that produce hemolysins considered to have an advantage?

Blood Agar and Hemolysis

Blood agar is an enriched media composed of tryptic soy agar with 5% sheep's blood added to it.
It is used as a differential media in the medical microbiology lab.
Gram-positive cocci can hemolyze (lyse) red blood cells and hemoglobin due to the production of hemolysins.
Hemolysins are exotoxins that cause red blood cells to burst open, releasing iron bound to hemoglobin molecules.

Types of Hemolysis

Hemolysis β (beta) is complete destruction of red blood cells and hemoglobin, resulting in a clearing of the blood agar.
Hemolysis β is characterized by a clear area around the inoculated organism on the blood agar plate.
Hemolysis α (alpha) is partial destruction of red blood cells and hemoglobin, resulting in a green appearance on the blood agar surface.
Hemolysis Υ (gamma) is non-hemolysis, where the organism grows on the agar surface without affecting the red blood cells.

Importance of Hemolysis

Iron is a limiting nutrient for many organisms, and hemolysin production provides an advantage for those organisms.
Hemolysin production allows organisms to access iron bound to hemoglobin molecules within red blood cells.

Explore the use of blood agar as a differential media in medical microbiology labs. Learn about the ability of Gram-positive cocci to hemolyze red blood cells and hemoglobin through the production of hemolysins. Test your knowledge on the targeting of iron by these organisms.