Test Procedure
1. Process each specimen as appropriate, inoculate directly onto the surface of the medium. Streak for
isolation with inoculating loop, stab agar several times to deposit beta-hemolytic streptococci beneath agar
surface. Subsurface growth will display the most reliable hemolytic reactions owing to activity of both
oxygen-stable and oxygen-labile streptolysins.6
2. Incubate plates aerobically, anaerobically, or under conditions of increased CO2 (5 - 10%) in accordance
with established laboratory procedures.
Results
Examine medium for growth and hemolytic reactions after 18 - 24 and 48 hours incubation. There are four
types of hemolysis on blood agar media described as:7
1. Alpha hemolysis () is the reduction of hemoglobin to methemoglobin in the medium surrounding the
colony. This produces a green discoloration of the medium.
2. Beta hemolysis () is the lysis of red blood cells, producing a clear zone surrounding the colony.
3. Gamma hemolysis (γ) indicates no hemolysis. No destruction of red blood cells occurs and there is no
change in the medium.
4. Alpha-prime hemolysis (ά) is a small zone of complete hemolysis surrounded by an area of partial lysis.