Vibrio vulnificus: Review of Mild to Life-threatening Skin Infections
Vibrio vulnificus is a motile, gram-negative, halophilic, aquatic bacterium that is part of the normal estuarine microbiome and typically is found in warm coastal waters. Infection with the pathogen typically is due to consumption of contaminated seafood or exposure to contaminated seawater. Vibrio vulnificus has a mortality rate of almost 33% in the United States and is responsible for more than 95% of seafood-related deaths in the United States. Vibrio vulnificus can cause a vast spectrum of diseases, such as gastroenteritis, cellulitis, necrotizing fasciitis, and sepsis. Gastroenteritis is self-limited, whereas septicemia often is fatal. Gastroenteritis and septicemia are caused by ingestion of contaminated shellfish, whereas wound infections and necrotizing fasciitis are caused by exposure to contaminated seawater or handling of contaminated seafood. Septicemia is the most common presentation of V vulnificus and accounts for the most fatalities from the bacteria. Prompt diagnosis and treatment are vital to prevent mortality. It is important to keep V vulnificus on the differential when a patient presents with bullae or cellulitis or has a history of raw seafood consumption or exposure to brackish water, as missing the diagnosis could lead to necrotizing fasciitis, sepsis, and death.
Practice Points
- Vibrio vulnificus infection should be high on the differential for patients who present with chronic liver disease and immunosuppression; a history of raw seafood consumption or exposure to brackish water; and bullae, cellulitis, necrotic lesions, or sepsis.
- Time to treatment is directly proportional to mortality rates in V vulnificus infections, and prompt treatment with antibiotics, wound care, debridement, and supportive measures is necessary to decrease mortality rates.
- The incidence of V vulnificus infection is rising in the United States, likely due to a combination of factors, including an aging population with multiple comorbidities, improvements in diagnosis, and climate change.
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
