Blood Agar Media Principle
Haemolysins are exotoxins produced by bacteria that lyse red blood cells. The haemolytic reaction can be visualized on blood agar plates. This media is used for cultivation of fastidious organisms and studying haemolytic reactions. It provides improved and enhanced haemolysis. On blood agar plates colonies of haemolytic bacteria may be surrounded by clear, colourless zone where the red blood cells have been lysed and the haemoglobin destroyed to a colourless compound. This is beta haemolysis. Other types of bacteria can reduce haemoglobin to methaemoglobin which produces a greenish zone around the colonies and is called alpha haemolysis. Gamma haemolysis is no haemolysis where no change in the medium is observed.
S.aureus will show beta hemolysis.
