This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Spleen, Subject name: Surgery
[{'content': 'Most common organism to cause OPSI \nSelect and explain. \nA. Streptococcal pneumonia, B. H. influenza, C. Mycobacterium TB, D. Babesia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans (a) Streptococcal pneumoniaRef Sabiston page 1568/20th edition* 50-90% cases of OPSI is due to streptococcal pneumonia.* PPV23 vaccine is given nowadays 2 weeks prior to elective surgery', 'role': 'assistant'}]