<prompt> Most common cause of native valve endocarditisStaphylococcus aureusCoagulase negative staphylococcusStreptococcusEnterococcus  <response>: 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. AureusM.C. cause of early-onset prosthetic valve endocarditis 2 mts 2-12 mts Coagulase-negative staphylococciM. C. cause of late-onset prosthetic valve endocarditis 12 mts Streptococci e.g. streptococcus viridansM.C. cause of endocarditis in I. V drug abusers Staph aureus. 