Because of the particulars of their blood supply, the tibia, femur, humerus, vertebra, the maxilla, and the mandibular bodies are especially susceptible to osteomyelitis. Abscesses of any bone, however, may be precipitated by trauma to the affected area. Many infections are caused by "Staphylococcus aureus", a member of the normal flora found on the skin and mucous membranes. In patients with sickle cell disease, the most common causative agent is "Salmonella", with a relative incidence more than twice that of S. aureus.