Osteomyelitis, an infection of bone, is caused most commonly by pyogenic bacteria and mycobacteria. As a useful framework for evaluating a patient and planning treatment, cases are classified on the basis of the causative agent; the route by which organisms gain access to bone; the duration of infection; the anatomic location of infection; and the local and systemic host factors that have a bearing on pathogenesis and outcome. Pathogenesis and Pathology Microorganisms enter bone by hematogenous dissemination, by spread from a contiguous focus of infection, or by a penetrating wound. Trauma, ischemia, and foreign bodies enhance the susceptibility of.