The organism that most commonly causes infective endocarditis is
Streptococcus sanguis is most common species in Viridans streptococcus to cause infective endocarditisReference: Jawetz, Melnick, & Adelberg's Medical Microbiology; 27th edition
Streptococcus mitis
Streptococcus viridians
Staphylococcus aureus
Staphylococcus pyogens
Bacteriology