The usual concentration of blood used for blood agar medium is: September 2004

Ans. A i.e. 10% Blood agar plate (BAP) Blood agar plate (BAP) contains mammalian blood (usually sheep or horse), typically at a concentration of 5-10%. BAP are enriched, differential media used to isolate fastidious organisms and detect haemolytic activity. Beta-hemolytic activity will show lysis and complete digestion of red blood cell contents surrounding colony. Examples include Streptococcus haemolyticus. Alpha-hemolysis will only paially lyse (the cells are either lysed or not- it is the digestion that may be incomplete) the hemoglobin and will appear green or brown (due to the conversion hemoglobin to methemoglobin). An example of this would be Streptococcus viridans. Gamma-hemolysis (or non-hemolytic) is the term referring to a lack of hemolytic activity. Contains meat extract, tryptone, sodium chloride and agar.