Laboratory Studies
See the list below:
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Gram stain: A Gram stain of fluid from the central hemorrhagic pustule or bulla can rapidly indicate the diagnosis. If no fluid is present, the eschar should be elevated and the underlying tissue swabbed for a Gram stain.
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Blood cultures: Two specimens should be collected prior to initiating antibiotic therapy. The optimal time of collection is during temperature spikes. Sensitivity studies should be performed on isolated organisms.
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Urine culture
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Skin biopsy: One 4- to 5-mm deep skin biopsy specimen should be obtained and placed in formalin fixative. Specimens should be stained with tissue Gram stain in addition to standard hematoxylin and eosin. Staining with special stains (eg, periodic acid-Schiff, methamine silver, Fite stains) should be performed to rule out other organisms that may cause ecthyma gangrenosum (EG)–like lesions.
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Tissue cultures: A second skin biopsy specimen should be placed in a sterile container for tissue culture. Specimens should be tested for bacteria, fungus, yeast, and mycobacteria. Preservative-free anesthetics and saline should be used for the procedure. Sensitivity studies should be performed on isolated organisms.
Imaging Studies
In a confirmed diagnosis of ecthyma gangrenosum (EG) of the plantar foot, magnetic resonance imaging (MRI) showed edema of the skin, subcutaneous fat, deep and superficial fascia, and plantar muscles. The postcontrast fat-suppressed images showed a geographic pattern of absent enhancement, which was consistent with muscle ischemia and/or necrosis. Deep fascial enhancement was absent; this is in contrast to necrotizing fasciitis, which on MRI demonstrates fascial enhancement after contrast administration. [25]
Histologic Findings
Skin biopsy specimens of ecthyma gangrenosum (EG) lesions show a necrotizing hemorrhagic vasculitis with few inflammatory cells but many surrounding bacilli. In sections stained with Gram stain, gram-negative rods are numerous in the media and adventitia of the necrotic vessels, but typically spare the intima. [26] Extravasation of blood, edema, and necrosis are seen around the involved vessels.
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Violaceous plaques and necrotic ulcers on the abdomen of a renal transplant patient. Tissue cultures were positive for Pseudomonas aeruginosa.
