This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infection of Bones & Joints, Subject name: Orthopaedics
[{'content': 'Most Commmon cause of chronic osteomyelitis - \nSelect and explain. \nA. Staphylococcus aureus, B. Streptococcus pyogenes, C. Mycobacterium tuberculosis, D. Staphylococcus epidermidis', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Staphylococcus aureus o Chronic osteomyelitis is nearly always a sequel to acute osteomyelitis,o Occasionally infection is subacute or chronic from the begining.o As with acute osteomyelitis, the most common causative organism is staphylococcus areus.", 'role': 'assistant'}]