Osteomyelitis is infection of the bone, usually by a pus-forming bacteria.
All bacterial osteomyelitis starts as acute infection.
If untreated or unsuccessfully treated after 6 weeks, by definition, it becomes chronic osteomyelitis. In the discussion that follows, we will confine ourselves to infection from the blood stream - the hematogenous type. The responsible bacteria differs in different age groups. In the neonate, the bacteria is usually Hemophilus influenzae . In older infants and children, it is often Staphylococcus aureus.