This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'An infant had a high-grade fever and respiratory distress at the time of presentation to the emergency room. The sputum sample showed gram-positive cocci having an a hemolytic activity. The suspected pathogen is susceptible to which of the following agent: \nSelect and explain. \nA. Novobiocin, B. Bacitracin, C. Oxacillin, D. Optochin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Sputum showing gram-positive cocci with alpha-hemolytic activity in a patient with high-grade fever and respiratory distress is suggestive of pneumococcal pneumonia which shows optochin susceptibility. Both pneumococcus and Streptococcus viridans produce alpha-hemolysis on blood agar. Optochin sensitivity test is done to differentiate Pneumococcus from commensal like Streptococcus viridans. Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition', 'role': 'assistant'}]