This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology Pa 1 (Gram Positive Cocci, Gram Negative Cocci), Subject name: Microbiology
A patient of RHD developed infective endocarditis after dental extraction. Most likely organism causing this is - 
Select and explain. 
A. Streptococcus viridans, B. Streptococcus pneumoniae, C. Streptococcus pyogenes, D. Staphylococcus aureus
A: Streptococcus viridans
Answer: A: Streptococcus viridans 
Explanation: Viridans streptococci Commensals in the mouth and upper respiratory tract. Cause transient bacteremia following tooth extraction or other dental procedures; -MC cause of subacute endocarditis: Streptococcus Viridans - MC Streptococcal species in Viridans group causing endocarditis: S. sanguis mc cause of Native valve endocarditis : S. aureus