It is not possible to sterilise whole blood products and therefore they must be collected aseptically. Horse and sheep blood are the most widely used animal blood products in culture media. The choice of which type of blood to use with culture media is largely traditional, with much of continental Europe preferring sheep blood, whilst the UK and certain parts of the Commonwealth prefer horse blood. Defibrinated sheep cells are aseptically collected whole sheep blood that has been processed to remove fibrin. There are no additives or preservatives in this product. Defibrination is now accepted as the best method of preventing blood clotting. It must be carried out immediately after drawing the blood and the agitation must be sufficient to denature the fibrinogen but not to cause rupture of the erythrocytes and haemolysis. The haemolytic reactions of sheep blood are not identical to the reactions of horse blood and blood agar media designed for sheep blood may not be satisfactory with horse blood and vice versa.
Defibrinated Sheep Blood
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|Streptococcus pneumoniae||NCTC 12977||Grey / green colonies with α-haemolysis|
|Streptococcus pyogenes||NCTC 12696||White colonies with β-haemolysis|
|Staphylococcus aureus||NCTC 12981||White colonies with double zone of weak β-haemolysis|
|Escherichia coli||NCTC 12241||Grey colonies|