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
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 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.