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
Eight months after prosthetic valve replacement, most common organism causing infective endocarditis is: 
Select and explain. 
A. Staph. epidermidis, B. Strep. viridans, C. Staph. aureus, D. HACEK
A: Staph. epidermidis
Answer: A: Staph. epidermidis 
Explanation: Ans. (a) Staph. epidermidis Coagulase negative staphylococci is the most common cause of endocarditis in posthetic value recepients with in one year of surgery.