This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Most Commmon cause of chronic osteomyelitis ? 
Select and explain. 
A. Staphylococcus aureus, B. Streptococcus pyogenes, C. Mycobacterium tuberculosis, D. Staphylococcus epidermidis
A: Staphylococcus aureus
Answer: A: Staphylococcus aureus 
Explanation: Ans. is 'a' i.e., Staphylococcus aureus Chronic osteomyelitis is nearly always a sequel to acute osteomyelitis. Occasionally infection is subacute or chronic from the begining. As with acute osteomyelitis, the most common causative organism is staphylococcus areus.