A wound culture and blood culture should be taken immediately if V vulnificus is suspected.8,11 A wound culture using discharge or fluid from necrotic or bullous lesions should be analyzed via gram stain.8,9 Gram stains of V vulnificus show short, slim, curved gram-negative rods under light microscopy.9,20 Special stains also can be done on cultures; V vulnificus is an oxidase-positive, lactose-positive, lysine-positive, salicin-positive, and arginine-negative organism. This knowledge can help differentiate V vulnificus from other gram-negative rods.13 Blood cultures will be positive in approximately 97% of patients with primary septicemia and 30% of patients with septicemia secondary to V vulnificus wound infections.3,9
Histologically, perilesional skin biopsies show epidermal necrosis with dermal and subcutaneous inflammation.12,17 There typically is an inflammatory infiltrate with neutrophilic abscesses and extensive tissue destruction in the subcutaneous tissue extending into the deep dermis.12,17 The superficial dermis is edematous but can lack the inflammatory infiltrate found in the subcutaneous tissue.17 Subepidermal bullae can form with numerous organisms within the fluid of the bullae. There also may be evidence of leukocytoclastic vasculitis with accompanying vessel wall necrosis. Fibrin clot formation and extravasated red blood cells may be visualized with few inflammatory cells but numerous organisms around the involved vessels.17
Management
Early diagnosis and treatment are vital.5,17 Cultures should be taken before aggressive treatment is started.3 Treatment is multifaceted; it requires antibiotics and wound care, except in cases of self-limited gastroenteritis.2,11 Aggressive debridement, fasciotomy, amputation, and supportive measures also may be necessary depending on the patient’s presentation.2,3,8,9 Establishing 2 peripheral intravenous lines is important in case rapid resuscitation becomes necessary.
Antibiotics
Primary cellulitis wound infections should be treated with doxycycline or a quinolone. If untreated, the wound can rapidly progress to necrotizing fasciitis.11 For necrotizing fasciitis and septicemia, broader-spectrum antibiotics are needed. For adults, ceftazidime plus doxycycline is the mainstay of antibiotic treatment for V vulnificus.2,9,11 For children, trimethoprim-sulfamethoxazole plus an aminoglycoside is preferred (Table).2,11
Antibiotic treatment has become more difficult as resistance arises. Antibiotic resistance likely is due to extensive antibiotic use in health care along with the agriculture and aquaculture industries using prophylactic and therapeutic antibiotics that wash into or are directly added to marine waters, where V vulnificus resides. Thus, antibiotic treatment should be tailored to the resistance profile of V vulnificus in various regions; for example, ceftazidime has an intermediate resistance profile in the United States, so cefotaxime and ceftriaxone may be better options.2