<prompt> Acute pyogenic osteomyelitis is caused byStaph, aureusStrepto. pneumoniaPneumococcusE. coli  <response>: 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 