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.
Immunosuppression
Patients who are immunocompromised and those with chronic liver disease are at an increased risk of infection because of neutrophils having decreased phagocytic activity.4
Diabetes Mellitus
Patients with diabetes mellitus may have peripheral neuropathy and may be unaware of pre-existing wounds that serve as entry points for V vulnificus.12
Etiology
Vibrio vulnificus infects humans via seafood consumption and handling as well as exposure to contaminated water.2,5 With respect to seafood consumption, raw shellfish are the primary type of seafood that harbor high levels of V vulnificus.5 Oysters are the most common etiology, but consumption of crabs, clams, and shrimp also can lead to infection.5,7Vibrio vulnificus contamination does not change the appearance, taste, or odor of shellfish, making it hard to detect.8 An inoculate of 1 million bacteria typically is necessary for infection after consumption.5 Contaminated seawater is another primary cause of V vulnificus infection. When open wounds are exposed to seawater harboring the bacteria, wound infections can arise.7 Infections can be acquired when swimming, fishing, or participating in water sports. Wound infections also occur while handling contaminated seafood, such as oyster shucking.5 There is a short incubation period for V vulnificus infections; the onset of symptoms and clinical outcome typically occur within 24 hours.5
,Clinical Presentation
Vibrio vulnificus infections can have numerous clinical presentations, including gastroenteritis, wound infections, necrotizing fasciitis, and sepsis.1,8 There also is a spectrum of clinical outcomes; for instance, gastroenteritis typically is self-limited, whereas necrotizing fasciitis or sepsis can be fatal.2
Gastroenteritis
Vibrio vulnificus gastroenteritis is due to ingestion of contaminated shellfish.2,9 Symptoms typically are mild to moderate and include nausea, vomiting, diarrhea, fever, chills, abdominal pain, and cramping.2,4,8 Cases likely are underreported in the United States because gastroenteritis is self-limited, and many patients do not seek treatment.2,11
Wound Infections
Wound infections with V vulnificus have a cutaneous port of entry. Exposure to contaminated seawater or seafood can inoculate an open wound, leading to infection.7,8 Wound infections usually stem from 1 of 2 routes: (1) a pre-existing open wound gets infected while the patient is swimming in contaminated water, or (2) a traumatic injury occurs while the patient is handling contaminated shellfish, knives, or fishhooks. Many shellfish, such as oysters, have sharp points on their shells that can lacerate the skin.8 A wound on the hand can be contaminated by V vulnificus while handling contaminated seafood (eg, oyster shucking).13 Minor abrasions should not be dismissed; in fact, a small puncture or skin break often acts as the port of entry.9,11 Wound infections tend to arise within 7 days of exposure, though they can manifest up to 12 days after exposure.8 Wound infections can present as cellulitis, bullae, or ecchymoses.7 Lesions are exquisitely tender, and the skin is erythematous with marked surrounding soft tissue edema.3,4,8 Cellulitis typically arises first, with hemorrhagic bullae rapidly following.14 Lesions are limited to the affected extremity or area of inoculation.8 Systemic symptoms are rare, but fever and chills may accompany the infection.8,14 Unfortunately, lesions can become necrotic and progress rapidly to necrotizing fasciitis if left untreated.4,7,11 In these cases, secondary sepsis can occur.8
Necrotizing Fasciitis
Wound infections caused by V vulnificus can progress to necrotizing skin and soft tissue infections, such as necrotizing fasciitis and gangrene.5 Necrotizing fasciitis accounts for approximately one-third of V vulnificus infections.9 It usually stems from an open wound that is inoculated by contact with contaminated seafood or seawater.2,9 The wound infection begins as cellulitis with extreme tenderness, erythematous skin, and marked soft tissue edema, then rapidly progresses, becoming necrotic. These necrotic lesions present as black and purple eschars as the skin, blood supply, and subcutaneous tissues are infiltrated by the bacteria and destroyed. Lesions may have blistering or exudation. Many patients have accompanying systemic symptoms, including fever, chills, abdominal pain, diarrhea, hypotension, and sepsis.11,14 However, some patients may not present with systemic symptoms, so it is important to maintain a high index of suspicion even in the absence of these symptoms. The infection typically is limited to the affected extremity; necrotizing infections can lead to amputation and even death, depending on the extent of destruction and spread of the bacteria.11,13 The infection may spread beyond the inoculated extremity if the bacteria gains access to the bloodstream.8,9 In these cases, fulminant purpura or secondary septicemia can occur.8,15 Fatalityrates in the United States for necrotizing V vulnificus infections approach 30%.2 Necrotizing fasciitis accounts for approximately 8% of deaths associated with the pathogen in the United States.9
