Blood Agar, 5% Sheep Blood

This medium is both differential and enriched medium and used for the isolation, cultivation and detection of hemolytic activity of fastidious microorganisms like Streptococci, and Pneumococci. The Blood Agar (Base No. 2) medium contains highly nutritious extract and the 5 % blood supplement that provides additional use in isolation, cultivation, and determination of hemolytic reactions of fastidious pathogenic microorganisms. Hemolytic patterns may vary with the source of animal blood or type of base medium used. In sheep blood, nucleotidase destroys V factors preventing the growth of Hemophilus species on sheep blood agar unless other microorganisms, such as Staphylococci, provide the V factors. Small amounts of reducing sugars inhibit the expression of β-hemolytic, and β-hemolytic Streptococci may develop a green zone or ring of hemolysis.

A number of streptococcal species produce substances that lyses of the red cell wall releasing of hemoglobin. Such substances are referred to as hemolysins. The activity of streptococcal hemolysins, streptolysins, can be readily observed when the organisms are growing on a blood agar plate. Different streptococci produce different effects on the red blood cells in blood agar. Those that produce incomplete hemolysis and only partial destruction of the cells around colonies are called alpha-hemolytic Streptococci. Characteristically, this type of hemolysis is seen as a distinct greening of the agar in the hemolytic zone, and thus this group of streptococci has also been referred to as the viridans group. Species whose hemolysins cause complete destruction of red cells in the agar zones surrounding their colonies are said to be beta-hemolytic which are small opaque or semi translucent colonies surrounded by clear zones in a red opaque medium. Two types of beta lysins are produced; Streptolysin-O, an antigenic oxygen-labile enzyme and Streptolysin-S, a non-antigenic oxygen-stable enzyme. The hemolytic reaction is enhanced when blood agar plates are streaked and simultaneously stabbed to show subsurface hemolysis by Streptolysin-O in an environment with reduced oxygen tension. Some strains of Staphylococci, Escherichia coli, and other bacteria also may show beta-hemolysis. Some species of Streptococci do not produce hemolysins. Therefore, when their colonies grow on blood agar, no change is seen in the red blood cells around them. These species are referred to as nonhemolytic or gamma hemolytic streptococci.


Product NameCatalog #Quantity
Sheep Blood Agar mono plate, 90 x 15 mm CB9150P 10/pk
Sheep Blood Agar mono plate, 90 x 15 mm Glutamine & Phenol Red CB9151P 10/pk
Sheep Blood Agar Slant CB9150S 10/pk
Sheep Blood Broth CB9150B 10/pk


Quality Control



The following organisms are routinely used for testing for this medium.
Test OrganismsResults
Streptococcus pneumonia ATCC® 6305 Growth; alpha-hemolysis
aStreptococcus pyogenes ATCC® 19615 Growth; beta-hemolysis
aStaphylococcus aureus ATCC® 25923 Growth; beta-hemolysis
Escherichia coli ATCC® 25922 Growth
Enterococcus faecalis ATCC® 29212 Growth
Staphylococcus aureus ATCC® 33862 Growth
Streptococcus agalactiae ATCC® 12386 Growth; positive (enhanced arrowhead hemolysis)
Streptococcus pyogenes ATCC® 19615 Growth; negative (no enhanced arrowhead hemolysis)
aRecommended QC strains for User Quality Control according to the CLSI document M22 when applicable

User Quality Control



Check for signs of contamination and deterioration. Users of commercially prepared media may be required to perform quality control testing with at least one known organism to demonstrate growth or a positive reaction; and at least one organism to demonstrate inhibition or a negative reaction (where applicable).

Ingredients g/L

Blood Agar, 5% Sheep defibrinated bloodIngredients g/l (Final pH 7.3 +/- 0.2 at 25°C)Yeast extract5.0
Proteose peptone 15.0
Liver extract 2.50
Sodium Chloride 5.0
Sheep Blood (mL) 50.0
Agar (where applicable): 12.0
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