Clinical Manifestations
Clostridial wound infections may be divided into three categories: gas gangrene or clostridial myonecrosis, anaerobic cellulitis, and superficial contamination. Gas gangrene can have a rapidly fatal outcome and requires prompt, often severe, treatment. The more common clostridial wound infections are much less acute and require much less radical treatment; however, they may share some characteristics with gas gangrene and must be included in the differential diagnosis.
Gas gangrene is an acute disease with a poor prognosis and often fatal outcome (Fig. 18-1). Initial trauma to host tissue damages muscle and impairs blood supply. This lack of oxygenation causes the oxidation-reduction potential to decrease and allows the growth of anaerobic clostridia. Initial symptoms are generalized fever and pain in the infected tissue. As the clostridia multiply, various exotoxins (including hemolysins, collagenases, proteases, and lipases) are liberated into the surrounding tissue, causing more local tissue necrosis and systemic toxemia. Infected muscle is discolored (purple mottling) and edematous and produces a foul-smelling exudate; gas bubbles form from the products of anaerobic fermentation. As capillary permeability increases, the accumulation of fluid increases, and venous return eventually is curtailed. As more tissue becomes involved, the clostridia multiply within the increasing area of dead tissue, releasing more toxins into the local tissue and the systemic circulation. Because ischemia plays a significant role in the pathogenesis of gas gangrene, the muscle groups most frequently involved are those in the extremities served by one or two major blood vessels.
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Clostridial septicemia, although rare, may occur in the late stages of the disease. Severe shock with massive hemolysis and renal failure is usually the ultimate cause of death. The incubation period, from the time of wounding until the establishing of gas gangrene, varies with the infecting clostridial species from 1 to 6 days, but it may be as long as 6 weeks. Average incubation times for the three most prevalent infecting organisms are as follows: C perfringens, 10-48 hours; C septicum, 2-3 days; and C novyi, 5-6 days. Because the organisms need time to establish a nidus of infection, the time lag between wounding and the appropriate medical treatment is a significant factor in the initiation of gas gangrene.
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Like gas gangrene, clostridial cellulitis is an infection of muscle tissue, but here the infecting organisms invade only tissue that is already dead; the infection does not spread to healthy, undamaged tissue. Clostridial cellulitis has a more gradual onset than gas gangrene and does not include the systemic toxemia associated with gas gangrene. Pain is minimal, and although only dead tissue is infected, the disease can spread along the planes between muscle groups, causing the surrounding tissue to appear more affected than it actually is. Anaerobic cellulitis may cause formation of many gas bubbles, producing infected tissue that looks similar to the gaseous tissue of gas gangrene. Some tissue necrosis does occur, but it is caused by decreased blood supply and not invasion by the infecting organism. With adequate treatment, anaerobic cellulitis has a good prognosis.
Superficial contamination, the least serious of the clostridial wound infections, involves infection of only necrotic tissue. Usually, the patient experiences little pain, and the process of wound healing proceeds normally; however, occasionally an exudate may form and the infection may interfere with wound healing. Superficial wound contamination caused by clostridia usually involves C perfringens, with staphylococci or streptococci, or both, as frequent co-isolates.
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