General Concepts
Necrotizing Soft Tissue Infections
Etiology
Anaerobic microorganisms such as Bacteroides species, Peptostreptococcus species, and Clostridium species are largely responsible for these infections. Mixed infections by aerobic and facultative anaerobic organisms are common.
Pathogenesis
Susceptible persons have experienced trauma or surgery and frequently have diabetes and/or vascular insufficiency. Organisms gain entry via direct inoculation. Local hypoxia and decreased oxygen-reduction potentials favor anaerobic growth.
Clinical Manifestations
This signs of disease include production of tissue gas, a putrid discharge, tissue necrosis, fever, (occasionally) systemic toxicity, and absence of classic signs of inflammation.
Microbiologic Diagnosis
These infections are usually diagnosed by clinical presentation. Aerobic and anaerobic wound cultures help identify the major pathogens.
Prevention and Treatment
Immediate surgical debridement of all necrotic tissue is vital. High-dose parenteral antibiotic therapy should be started immediately. Hyperbaric oxygen therapy may be indicated.
Joint Infections
Etiology
Neisseria gonorrhoeae and S taphylococcus aureus are responsible for most cases of bacterial arthritis.
Pathogenesis
Joint infections are usually a result of hematogenous spread, but may also arise from traumatic inoculation or by extension from an adjacent focus of infection. Proteolytic enzymes of polymorphonuclear leukocytes, bacterial toxins, and pressure from joint swelling all contribute to the damage of articular surfaces.
Clinical Manifestations
Joint swelling. pain, warmth (inflammation), decreased range of motion, and fever are the classic symptoms. Disseminated gonococcal infections may also cause migratory polyarthritis, dermatitis, and tenosynovitis.
Microbiologic Diagnosis
Aspiration and culture of synovial fluid usually provides the definite diagnosis.
Prevention and Treatment
Gonococcal arthritis may be prevented by techniques used to decrease the risk for sexually transmitted disease. The treatment for all septic arthritides is administration of parenteral antibiotics. Some cases may require aspiration and/or surgical debridement.
Bone Infections
Etiology
Staphylococcus aureus is the most commonly isolated pathogen. Polymicrobic infections are frequent in contiguous-focus osteomyelitis.
Pathogenesis
Organisms may reach the bones by hematogenous spread, by direct extension from a contiguous focus of infection, or as a result of trauma. A cycle of increased pressure from infection, inflammation, local ischemia, and bone necrosis may establish itself and lead to a chronic infection.
Clinical Manifestations
Hematogenous osteomyelitis classically presents with high fever and pain around the involved bone. Sinus tracts with purulent drainage are evidence of chronic osteomyelitis.
Microbiologic Diagnosis
Bone biopsy and/or debridement cultures are mandatory with rare exceptions. Sinus tract cultures are unreliable.
Prevention and Treatment
Treatment consists of surgical debridement and long-term, culture-directed antimicrobial therapy. Hematogenous osteomyelitis in children may be treated with antibiotics alone.
