Types of Hemolysis Shown By Bacterial Cultures on Blood Agar

A bacterial species may show a pattern of hemolysis when grown on blood agar.

Test requirement: agar containing intact erythrocytes

Pattern of Hemolysis	Appearance	Type of Hemolysis
partial lysis	medium appears green, grey or brown	alpha
no hemolysis beneath or close to colonies; complete hemolysis beyond	no change beneath the culture but clearing further out	alpha-prime ("wide zone")
complete lysis	complete clearing of red blood cells beneath and surrounding colonies	beta
no hemolysis	no change	gamma (nonhemolyhtic)

Enzymes causing hemolysis may be affected by oxygen, so hemolysis may be better seen in:

(1) cultures grown anaerobically

(2) cultures grown in 5-7% carbon dioxide

(3) along stabs made into the agar when streaking the plates.

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