chapter  42
26 Pages

Imaging and Surgical Principles of Osteomyelitis and Pressure Ulcers

Osteomyelitis is a pyogenic bone infection that may be acute, subacute, and chronic. Infections may occur from haematogenous spread, spread from a contiguous source, direct

implantation, or after trauma or surgery. Aerobic Gram-positive cocci are the predominant microorganisms that colonise and acutely

infect breaks in the skin. Staphylococcus aureus and the haemolytic streptococci (groups A, C, and G, but especially group B) are the most commonly isolated pathogens. Chronic wounds develop a more complex colonising ora, including enterococci, various Enterobacteriaceae, obligate anaerobes, Pseudomonas aeruginosa, and, sometimes, other nonfermentative Gram-negative rods. Hospitalisation, surgical procedures, and, especially, prolonged or broad-spectrum antibiotic therapy may predispose patients to colonisation and/or infection with antibiotic-resistant organisms (e.g. methicillin-resistant S. aureus [MRSA] or vancomycin-resistant enterococci [VRE]). Although MRSA strains have previously been isolated mainly from hospitalised patients, communityassociated cases are now becoming common and are associated with worse outcomes in patients with diabetic foot infections. Acute infections in patients who have not recently received antimicrobials are often monomicrobial (almost always with an aerobic Gram-positive coccus), whereas chronic infections are often polymicrobial.1