BLOOD AGAR BASE (INFUSION AGAR)

Blood Agar Base is a highly nutritious medium generally used as a basal medium for preparing blood agar by supplementation with blood. It can also be used as general-purpose media without the addition of blood. Blood Agar Base media can be used with added phenolphthalein phosphate for the detection of phosphate producing Staphylococci, with added salt and agar for assessment of surface contamination on equipment and pig carcass and to determine salinity range of marine Flavobacteria. It can also be used for preparation of Salmonella Typhi antigens. Blood Agar Base is recommended by APHA and Standard Methods for testing of food samples.
Addition of blood makes the medium more nutritious by providing additional growth factors required by fastidious organisms. It also helps in visualizing the haemolytic reactions. However, haemolytic reactions depend on the animal blood used. Sheep blood gives best results for Group A Streptococci. But sheep blood fails to support growth of Haemophilus haemolyticus since sheep blood is deficient in pyridine nucleotides. However, when horse blood is used H. haemolyticus colonies produce haemolysis and mimic Streptococcus pyogenes.

for isolation and cultivation of fastidious pathogenic microorganisms after addition of blood