What streptococcus causes infective endocarditis?

Endocarditis: It is estimated that about 2/3 of the cases of endocarditis are caused by streptococcal bacteria. Streptococcal bacteria causing endocarditis include streptococcus viridans as well as groups a, c, and g streptococcal bacteria.

Alpha streptococci: Are the most common cause of this infection. The Alpha refers to the partial hemolysis found on a blood agar plate producing a green color as compared to the complete hemolysis of the beta strep. This green color is from where the term viridans streptococcus comes from. There is, however, no organism formally called streptococcus viridans.