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
Acute pyogenic osteomyelitis is caused by 
Select and explain. 
A. Staph, aureus, B. Strepto. pneumonia, C. Pneumococcus, D. E. coli
A: Staph, aureus
Answer: A: Staph, aureus 
Explanation: i.e. (Staph.aureus): (157-J. Maheshwari 3rd) (27-Apley 8th)* Staph, aureus is the commonest causative organism in acute osteomyelitis* Staph, aureus is the commonest causative organism in septic arthritis* Commonest site is metaphysis. This is because of the peculiar arrangement of the blood vessels in that area, which leads to relative vascular stasis, favouring bacterial colonization