A 28-year-old man with fever persisting for 3 weeks presented with tricuspid valve vegetation. The patient is an intravenous drug abuser. The most common cause of endocarditis in this patient is

Staphylococcus aureus is the most common cause of infective endocarditis among injection drug users. Microbiology of Infective Endocarditis Community-acquired Native valve endocarditis- Viridans group streptococci (VGS) Healthcare-associated Native valve endocarditis -Staphylococcus aureus Endocarditis in injection drug users- Staphylococcus aureus Early prosthetic valve endocarditis (<12 months after surgery)- Single most common causative organism: Viridans Streptococci and Overall most common cause: Coagulase-negative staphylococci (CoNS)* Late prosthetic valve endocarditis (>12 months after surgery)- Single most common causative organism: Viridans Streptococci and Overall most common cause: Coagulase-negative staphylococci (CoNS)* Cardiovascular implantable electronic device (CIED)- associated endocarditis- Staphylococcus aureus and coagulase-negative Staphylococci (CoNS)* *CoNS includes Staphylococcus epidermidis and other coagulase-negative types *Streptococci includes Viridans streptococci (VGS), Streptococcus gallolyticus (previously Streptococcus bovis biotype 1) and other nongroupable and groupable streptococci Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition