 |
Clostridial
soft-tissue infections include cellulitis, myositis, and clostridial
myonecrosis. They usually occur after trauma. Symptoms may include
edema, pain, gas with crepitation, foul-smelling exudates, intense
coloration of the site, and progression to shock and renal failure. Diagnosis
is by inspection and smell, confirmed by culture. Treatment is with
penicillin and surgical debridement. Hyperbaric O2 is
sometimes beneficial.
Clostridium perfringens is the most common strain involved. Infection develops hours or days after injury, usually in an extremity after severe crushing or penetrating trauma devitalizes tissue, creating anaerobic conditions. The presence of foreign material (even sterile) markedly increases the risk of clostridial infection. Infection also may occur in operative wounds, particularly in patients with underlying occlusive vascular disease. Spontaneous cases occur rarely, usually involving C.
septicum originating from occult colon perforation in patients with colon cancer, diverticulitis, or bowel ischemia. Infection typically, but not always, results in soft-tissue gas collection.
In proper conditions (low oxidation-reduction potential, low pH), as occur in devitalized tissue, infection progresses rapidly, from initial injury through shock, toxic delirium, and death within as little as 1 day.
Symptoms and Signs
Clostridial cellulitis occurs as a localized infection in a superficial wound, usually ≥ 3 days after injury. Infection may spread extensively along fascial planes, often with evident crepitation and abundant gas bubbling, but toxicity is much less severe than with extensive myonecrosis, and pain is minimal. Bullae frequently are evident, with foul-smelling, serous, brown exudate. Discoloration and gross edema of the extremity are rare. Clostridial skin infections associated with primary vascular occlusion of an extremity rarely progress to severe toxic myonecrosis or extend beyond the line of demarcation.
Clostridial myositis, suppurative infection of muscle without necrosis, is most common in parenteral drug users. It resembles staphylococcal pyomyositis and lacks the systemic symptoms of clostridial myonecrosis. Edema, pain, and frequently gas in the tissues occur. It spreads rapidly and may progress to myonecrosis.
In clostridial myonecrosis (gas gangrene), initial severe pain is common, sometimes even before other findings. The wound site may be pale initially, but it becomes red or bronze, often with blebs or bullae, and finally turns blackish green. The area is tensely edematous and tender to palpation. Crepitation is less obvious early than it is in clostridial cellulitis but is ultimately palpable in about 80%. Wounds and drainage have a particularly foul odor.
With progression, the patient appears toxic, with tachycardia, pallor, and hypotension. Shock and renal failure occur, although the patient often remains alert until the terminal stage. Unlike clostridial uterine infection, overt hemolysis is rare in gas gangrene of the extremities, even in terminally ill patients. Whenever massive hemolysis occurs, mortality of 70 to 100% can be expected due to acute renal failure and septicemia.
Diagnosis
Early suspicion and intervention are essential. Clostridial cellulitis responds well to treatment, but myonecrosis has a mortality rate of ≥ 40% with treatment and 100% without.
Although localized cellulitis, myositis, and spreading myonecrosis may be clinically distinct, differentiation often requires surgical exploration. In myonecrosis, muscle tissue is visibly necrotic; the affected muscle is a lusterless pink, then deep red, and finally gray-green or mottled purple and does not contract on stimulation. X-rays may show local gas production, and CT and MRI delineate the extent of gas and necrosis.
Wound exudate should be cultured for anaerobic and aerobic organisms. Because of their short generation time, anaerobic cultures of Clostridia may be positive in as little as 6 h. However, other anaerobic and aerobic bacteria, including members of the Enterobacteriaceae family and Bacteroides
, Streptococcus, and Staphylococcus spp, alone or mixed, can cause clostridia-like severe cellulitis, extensive fasciitis, or clostridial myonecrosis (see Bacterial Skin Infections: Necrotizing Subcutaneous Infection). Also, many wounds, particularly if open, are contaminated with both pathogenic and nonpathogenic clostridia that are not responsible for the infection. The presence of clostridia is significant when Gram stain shows them in large numbers, few PMNs are found in the exudates, and free fat globules are demonstrated with Sudan stain. However, if PMNs are abundant and the smear shows many chains of cocci, an anaerobic streptococcal or staphylococcal infection should be suspected. Abundant gram-negative bacilli may indicate infection with one of the Enterobacteriaceae or a Bacteroides sp (see Anaerobic Bacteria: Mixed Anaerobic Infections). Detection of clostridial toxins in the wound or blood is useful only in the rare case of wound botulism (see Anaerobic Bacteria: Botulism).
Treatment
When clinical signs of clostridial infection are present, such as gas or myonecrosis, rapid, aggressive intervention is mandatory. Thorough drainage and debridement are as important as antibiotics; both should be instituted rapidly. Penicillin G is the drug of choice; 1 to 2 million units IV q 2 to 3 h should be given immediately for severe cellulitis and myonecrosis. Addition of clindamycin 600 mg IV q 6 h is beneficial. If gram-negative organisms are seen or suspected, a broad-spectrum antibiotic (eg, ticarcillin combined with clavulanate, ampicillin combined with sulbactam, or piperacillin combined with tazobactam) should be added.
Hyperbaric O2 therapy may be helpful in extensive myonecrosis, particularly in extremities, as a supplement to antibiotics and surgery. Hyperbaric O2 therapy may have potential to salvage tissue and lessen mortality and morbidity if started early but should not delay surgical debridement.
Last full review/revision November 2005
Content last modified November 2005
| |
