Drawing of Staphylococcus bacteria Age group Most common organisms Newborns (younger than 4 mo) Staphylococcus aureus, Enterobacter species, and group A and B Streptococcus species Children (aged 4 mo to 4 y) S. aureus, group A Streptococcus species, Haemophilus influenzae, and Enterobacter species Children, adolescents (aged 4 y to adult) S. aureus (80%), group A Streptococcus species, H. influenzae, and Enterobacter species Adult S. aureus and occasionally Enterobacter or Streptococcus species Sickle cell anemia patients Salmonella species are most common in patients with sickle cell disease. In children, the metaphyses, the ends of long bones, are usually affected. In adults, the vertebrae and the pelvis are most commonly affected. Acute<unk>  almost invariably occurs in children who are otherwise healthy, because of rich blood supply to the growing bones. When adults are affected, it may be because of compromised host resistance due to debilitation, intravenous drug abuse, infectious root-canaled teeth, or other disease or drugs (e.g., immunosuppressive therapy).<unk>  is a secondary complication in 1–3% of patients with pulmonary tuberculosis. In this case, the bacteria, in general, spread to the bone through the circulatory system, first infecting the synovium (due to its higher oxygen concentration) before spreading to the adjacent bone. In tubercular<unk> , the long bones and vertebrae are the ones that tend to be affected. Staphylococcus aureus is the organism most commonly isolated from all forms of<unk> . Bloodstream-sourced<unk>  is seen most frequently in children, and nearly 90% of cases are caused by Staphylococcus aureus. In infants, S. aureus, Group B streptococci (most common) and Escherichia coli are commonly isolated; in children from one to 16 years of age, S. aureus, Streptococcus pyogenes, and Haemophilus influenzae are common. In some subpopulations, including intravenous drug users and splenectomized patients, Gram-negative bacteria, including enteric bacteria, are significant pathogens. The most common form of the disease in adults is caused by injury exposing the bone to local infection. Staphylococcus aureus is the most common organism seen in<unk> , seeded from areas of contiguous infection. But anaerobes and Gram-negative organisms, including Pseudomonas aeruginosa, E. coli, and Serratia marcescens, are also common. Mixed infections are the rule rather than the exception. Systemic mycotic infections may also cause<unk> . The two most common are Blastomyces dermatitidis and Coccidioides immitis. In<unk>  involving the vertebral bodies, about half the cases are due to S. aureus, and the other half are due to tuberculosis (spread hematogenously from the lungs). Tubercular<unk>  of the spine was so common before the initiation of effective antitubercular therapy, it acquired a special name, Pott's disease. The Burkholderia cepacia complex has been implicated in vertebral<unk>  in intravenous drug users.
Osteomyelitis
Cellulitis
Osteoradionecrosis
Septic arthritis
Osteitis
Rheumatoid arthritis
Osteochondropathy
Neuropathic arthropathy