Background
Vibrio vulnificus is a gram-negative bacillus that affects only humans and other primates. Besides V vulnificus, the genus Vibrio contains more than 100 bacterial species; about 12 Vibrio species are linked to human infections, [1] including the organism that causes cholera (ie, Vibrio cholerae). (See Vibrio Infections.) The first documented case of disease caused by V vulnificus was in 1979.
V vulnificus is usually found in warm, shallow coastal salt water in temperate climates throughout most of the world. It is present in the Gulf of Mexico, along most of the East Coast of the United States, and along all of the West Coast of the United States. V vulnificus can be found in water, in sediment, in plankton, and in shellfish (eg, oysters, clams, and crabs).
In addition, brackish, fast-warming waters in the Baltic Sea region can facilitate proliferation of Vibrio species, including V vulnificus. [1] Global climate alterations may elevate water temperatures and increase the incidence of V vulnificus infections. [2] Identifying and forecasting environmental factors that conduce to the development of V vulnificus infections may be assisted by the use of machine learning. [3]
V vulnificus can survive in seawater and can produce wound infections, a potentially serious problem among Asian tsunami survivors, [4] as well as potentially fatal necrotizing fasciitis in them and in individuals with liver cirrhosis. [5] (See the image below.) This halophilic bacterium can also cause serious gastroenteritis after ingestion of raw seafood. [6] Genome sequencing has been performed. [7]
Vibrio infections. Early bullous lesions appear over dorsum of foot of patient with cirrhosis.
Pathophysiology
V vulnificus infects the body in either of the following two ways:
-
Ingestion of contaminated seafood (eg, raw oysters)
-
Exposure of an open wound to contaminated seawater
Healthy individuals typically experience vomiting, diarrhea, and abdominal pain within 16 hours of ingestion. Many patients develop distinctive bullous skin lesions. (See Presentation.) In immunocompromised individuals, particularly those with chronic liver disease (especially cirrhosis), immunosuppression, end-stage renal disease, and hematopoietic disorders, V vulnificus can cause life-threatening septic shock and blistering skin lesions. Those who are immunocompromised have a much higher risk of contracting V vulnificus infection and dying of overwhelming sepsis. [2]
The relatively low incidence of the disease suggests that not all strains of V vulnificus may be equally virulent. Data are consistent with the existence of two genotypes of the organism, with the C type being a strong indicator of potential virulence. [8] The biotype 3 group of V vulnificus may have emerged in Israel as a consequence of genome hybridization of two bacterial populations. The emergence of this clonal subgroup suggests that the fish aquaculture environment, and possibly human-made ecologic niches as a whole, may be a source of new pathogenic strains. [9]
Etiology
V vulnificus can be found in various types of seafood. It can grow rapidly in shellfish, owing to the ambient air conditions occurring with intertidal exposure. [10] An evaluation of 306 seafood samples, including shrimp and mussels, from supermarkets in Berlin found an overall Vibrio prevalence of 56%; the species most commonly found in the samples was Vibrio parahaemolyticus, with only 4% of the samples harboring V vulnificus. [11]
A study of Vibrio species isolated from retail shrimp in Hanoi found that 201 of 202 samples were positive for Vibrio, with most containing V parahaemolyticus (96.5%) and far fewer (1.5%) containing V vulnificus. [12] Sanitary working conditions and thorough cooking of shrimp should be encouraged.
Vibrio species are common in aquatic environments; a study of diseased freshwater and ornamental fish in Poland identified six Vibrio species. [13]
Epidemiology
US and international statistics
In the United States, V vulnificus infections are rare but underreported. Most cases are found in the Gulf Coast states and occur predominantly during warm weather months. Since 2007, V vulnificus has been difficult to culture from North Carolina oyster samples. It may be that oysters were colonized with a more salt-tolerant bacterium during the drought, displacing V vulnificus and possibly preventing recolonization. [14] Evaluation of the graveyard skeletons of two American Civil War soldiers revealed they may have died as a result of V vulnificus bloodstream infection (BSI). [15]
A 2008 from Japan that evaluated the frequency of V vulnificus infection, which is rare in that country, found that the prevalence varied in different districts. [16] A 2017 study from India found that 10 (38.5%) of 26 clam (Meretrix meretrix) samples obtained from the markets in the attractive tourist destination of Mangalore harbored V vulnificus. [17] Marine aquaculture has rendered V vulnificus infections relatively common all over the world. [18]
Age-, sex-, and race-related demographics
All ages are affected equally. Males and females are affected equally. All races are affected equally.
Prognosis
Most V vulnificus infections are acute and cause no long-term adverse effects. With proper treatment (ie, antibiotics), the prognosis is often excellent. It must be kept in mind, however, that this organism is the cause of more than 95% of seafood-related deaths in the United States and has the highest fatality rate of any food-borne pathogen. [19]
Although most patients with V vulnificus infection experience no long-term consequences, mortality may be as high as 50% in patients who develop septic shock as a consequence of such infection. A 2017 case report described a man who became infected with V vulnificus after swimming in the Gulf of Mexico 5 days after the completion of a leg tattoo. [20] The patient died of septic shock; his chronic liver disease was cited as a possible contributing factor.
In rare instances, skin infection can result in necrotizing fasciitis. V vulnificus necrotizing skin and soft-tissue infections may result in multiple organ failure and death. A prediction model to estimate the case-fatality rate has been proposed. [21]
A retrospective analysis of 30 patients with necrotizing fasciitis and sepsis caused by Vibrio species and initially treated with surgical debridement or immediate limb amputation showed that 11 (37%) died within several days of admission. [22] Mortality was higher in the V cholerae non-O1 group (57%) than in the V vulnificus group (30%). Other bad prognostic signs included a systolic blood pressure of 90 mm Hg or lower, decreased platelet counts, and leukopenia. The combination of hepatic dysfunction and diabetes mellitus was also associated with a poor outcome.
Predictive factors for mortality in primary BSI or wound infection caused by V vulnificus have been accessed by using a variety of parameters. A multivariate analysis indicated that the presence of hemorrhagic bullae/necrotizing fasciitis, primary BSI, a greater severity of illness, absence of leukocytosis, and hypoalbuminemia were significant risk factors for mortality in V vulnificus skin and soft-tissue infections. [23]
Patient Education
Patients who are immunocompromised should be counseled regarding means of preventing exposure to V vulnificus. The high mortality associated with this infection suggests that susceptible individuals should be forewarned by signs displayed in restaurants. Physicians should educate patients with chronic liver disease about the risk posed by raw oyster consumption. Additionally, harvesting methods that reduce contamination by V vulnificus should be used. [24]
-
Vibrio infections. Early bullous lesions appear over dorsum of foot of patient with cirrhosis.
