Vibrio vulnificus is a species of Gram-negative, motile, curved rod-shaped (vibrio), pathogenic bacteria of the genus Vibrio. Present in marine environments such as estuaries, brackish ponds, or coastal areas, V. vulnificus is related to V. cholerae, the causative agent of cholera. At least one strain of V. vulnificus is bioluminescent. Increasing seasonal ocean temperatures and low-salt marine environments like estuaries favor a greater concentration of Vibrio within filter-feeding shellfish; V. vulnificus infections in the Eastern United States have increased eightfold from 1988–2018.
Infection with V. vulnificus leads to rapidly expanding skin infections by entering a wound causing cellulitis or even sepsis. V. vulnificus is also a source of foodborne illness. It was first isolated as a source of disease in 1976.
Strains
Vibrio vulnificus is a species of Gram-negative, motile, curved rod-shaped (bacillus), pathogenic bacteria of the genus Vibrio. Present in marine environments such as estuaries, brackish ponds, or coastal areas, V. vulnificus is related to V. cholerae, the causative agent of cholera. The most harmful strains of V. vulnificus documented have been observed in three different forms. The first is in an anti-phagocytic polysaccharide capsule that protects the bacteria. By encapsulating the bacteria, phagocytosis and opsonization can not occur, thus allowing the bacteria to continue throughout the organism it is in. The second way that V. vulnificus has been most harmful is with some of the toxins that it creates. These toxins are not part of the infection that V. vulnificus causes but instead they are part of a secondary infection in the gastrointestinal tract that most certainly will lead to systemic infection. Lastly, V. vulnificus has been seen to cause more harm in patients who have higher levels of iron.
Natural transformation
Natural transformation is a bacterial adaptation for DNA transfer between individual cells. V. vulnificus was found to become naturally transformable during growth on chitin in the form of crab shells. The ability to now carry out transformation experiments in the laboratory should facilitate molecular genetic analysis of this opportunistic pathogen.
Signs and symptoms
Vibrio vulnificus is an extremely virulent bacterium that can cause three types of infections: Acute gastroenteritis from eating raw or undercooked shellfish: V. vulnificus causes an infection often incurred after eating seafood, especially raw or undercooked oysters. It does not alter the appearance, taste, or odor of oysters. Symptoms include vomiting, diarrhea, and abdominal pain. Necrotizing wound infections can occur in injured skin exposed to contaminated marine water. V. vulnificus bacteria can enter the body through open wounds when swimming or wading in infected waters, or by puncture wounds from the spines of fishes such as stingrays. People may develop a blistering dermatitis sometimes mistaken for pemphigus or pemphigoid. Invasive sepsis can occur after eating raw or undercooked shellfish, especially oysters. V. vulnificus is 80 times more likely to spread into the bloodstream in people with compromised immune systems, especially those with chronic liver disease. When this happens, severe symptoms including blistering skin lesions and septic shock can sometimes lead to death. This severe infection may occur regardless of whether the infection began from contaminated food or an open wound.
Among healthy people, ingestion of V. vulnificus can cause vomiting, diarrhea, and abdominal pain. In someone with a compromised immune system, particularly those with chronic liver disease, it can infect the bloodstream, causing a severe and life-threatening illness characterized by fever and chills, decreased blood pressure (septic shock), and blistering skin lesions. While men have been shown to be more at risk from this infection than women, co-morbidities such as alcoholic cirrhosis and diseases affecting the endocrine system (diabetes, rheumatoid arthritis, etc.) put a person far more at risk to develop infection from V. vulnificus.
Pathogenesis
Capsule: V. vulnificus has a capsule, made of polysaccharides, and is thought to protect against phagocytosis. The capsule also aids the bacteria in escaping opsonization. Different strains of the bacteria are capable of shifting through the unencapsulated and encapsulated forms. Mouse models have shown that the unencapsulated forms are avirulent. These same strains however, are shown to have a higher predisposition to shift to the virulent encapsulated form when taken up by oysters.