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
[{'content': 'A patient of RHD developed infective endocarditis after dental extraction. Most likely organism causing this is - \nSelect and explain. \nA. Streptococcus viridans, B. Streptococcus pneumoniae, C. Streptococcus pyogenes, D. Staphylococcus aureus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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', 'role': 'assistant'}]