Microbiology Primer: Hemolysis

	Unified Program in Infectious Diseases, Montefiore Medical Center and Albert Einstein College of Medicine.

Microbiology Primer: Hemolysis

There are two types of hemolysis on blood agar plates: alpha, beta, and gamma (gamma hemolysis is actually no hemolysis).

Alpha hemolysis Beta hemolysis Gamma hemolysis

Streptococcus pneumoniae Streptococcus pyogenes (Group A beta-hemolytic strep) Enterococcus faecalis (formerly Group D Strep)
Alpha hemolysis close Beta hemolysis close Gamma hemolysis close
There is a darkening of the agar. There is complete lysis of red cells. Light will shine through an area of beta-hemolysis. In the thick part of the streak on this plate, one can see the label through the clearing. There is no change of the agar. But note: Some strains of Strep exhibit alpha hemolysis limited to underneath the colony. These may be initially misidentified as gamma Strep.

For comparison, here are the above three strains streaked out on the same plate.
Alpha/Beta/Gamma

Certain species of bacteria are weakly beta-hemolytic but synergize with a strain of Staph to produce intense beta-hemolysis. This is called the CAMP test (after the initials of its inventors). One such species is Group B Strep (Streptococcus agalactiae).

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id/micro/hemolysis.htm/Created 21 Apr 1999/Last Modified 4 October 2001/Craig Werner/ werner@aecom.yu.edu

Alpha hemolysis	Beta hemolysis	Gamma hemolysis

Streptococcus pneumoniae	Streptococcus pyogenes (Group A beta-hemolytic strep)	Enterococcus faecalis (formerly Group D Strep)

There is a darkening of the agar.	There is complete lysis of red cells. Light will shine through an area of beta-hemolysis. In the thick part of the streak on this plate, one can see the label through the clearing.	There is no change of the agar. But note: Some strains of Strep exhibit alpha hemolysis limited to underneath the colony. These may be initially misidentified as gamma Strep.

For comparison, here are the above three strains streaked out on the same plate.


Certain species of bacteria are weakly beta-hemolytic but synergize with a strain of Staph to produce intense beta-hemolysis. This is called the CAMP test (after the initials of its inventors). One such species is Group B Strep (Streptococcus agalactiae).