Most common cause of native valve endocarditis

Infective endocarditis in intravenous drug abusers commonly involves the tricuspid valve and are caused by Staphylococcus aureus. M. C. cause of native valve endocarditis → Staph. Aureus M.C. cause of early-onset prosthetic valve endocarditis (< 2 mts & 2-12 mts) → Coagulase-negative staphylococci M. C. cause of late-onset prosthetic valve endocarditis (> 12 mts) → Streptococci (e.g. streptococcus viridans) M.C. cause of endocarditis in I. V drug abusers → Staph aureus.