This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
A 23 year old patient had fever since 2 weeks presents with mitral valve vegetation. Patient is a intravenous drug abuser. Most common cause of endocarditis in this patient is : 
Select and explain. 
A. S.aureus, B. S.epidermidis, C. Enterococcus, D. Viridans Streptococci
C: Enterococcus
Answer: C: Enterococcus 
Explanation: i.v. drug abusers

Lt. sided endocarditis – Enterococcus
Rt. sided endocarditis – S.aureus