The hemolytic reaction is particularly useful in the differentiation of the Streptococci. The hemolytic reaction is determined on agar media containing 5% animal blood. The most commonly used base medium is trypticase soy agar and the most commonly used blood is sheep blood. The reason for the use of trypticase soy base is that it supports the growth of all the bacteria listed in Table 2. Other base media may be substituted if control strains of all genera are tested for growth. Sheep blood is used because of the convenience in testing throat swabs for ß-hemolytic streptococci. Sheep blood does not support the growth of Haemophilus haemolyticus which appears similar to streptococci on agar containing rabbit, horse, or human blood.
Tested organisms