On standard wool sheep blood media, both Group B
streptococcus and Group A streptococcus grow as translucent
colonies exhibiting b-hemolysis. Group A streptococcus colonies
tend to be smaller (,0.5 mm) with a sharply demarcated zone of
hemolysis surrounding each colony and extending beyond the
colony, while Group B streptococcus colonies are slightly larger
(.0.5 mm) with soft b-hemolysis directly underneath the colony.
These characteristics of their growth and hemolytic pattern on
wool sheep blood agar were also apparent on both citrated and
defibrinated hair sheep blood agar