Question

A detailed note on hemolysis

Answer 1

Answer:

Hemolysis is the breakdown of blood cells (haem =blood and lysis =breakdown) by some bacteria which is used in their classification, mostly performed on blood agar. Such bacteria produce enzymes for lysing the blood, typically called as hemolysin and depending on the structure and type of lysin produced, one may chategorise these bacteria into 3 classes:

Alpha hemolysis

Bacteria that produce Alpha-hemolysin cause a partial break down of the red blood cells and cause a greenish color on the surface of the agar plate, around the colonies due to the build up of bile and other metabolites upon RBC breakdown. An example of alpha hemolysis causing bacteria would be Streptococcus spp. (S. mitis).

Beta Beta-hemolysis

Beta-hemolysin producing bacteria breaks down the red blood cells and the hemoglobin contained within it, completely. This results in the formation of a clear zone around the bacterial growth referred to as β-hemolysis.

A good example of a β-hemolysis causing bacteria is S. pyogenes.

Gamma Hemolysis

Bacteria that grow on blood agar surface but are unable to breakdown RBC or metabolize hemoglobin are classified into this type. They show no zone around their growth.

S. salivarius is a well known γ-hemolytic (= non-hemolytic) bacteria.