Columbia Agar with 5% Horse Blood 20. This agar is a highly nutritious general purpose medium for the isolation and cultivation of nonfastidious and fastidiousmicroorganisms from clinical and non-clinical materials. It should be noted that beta-hemolytic reactions depend on the typeof blood added; as an example, enterococci which only very rarely hemolyse sheep blood, will produce a well visible betahemolysis on horse blood. Staphylococcus aureus which is usually beta hemolytic on sheep blood, will often be non-hemolyticon horse blood.