|False-color SEM image of Vibrio vulnificus|
(Reichelt et al. 1976)
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. Infection with V. vulnificus leads to rapidly expanding cellulitis or septicemia.:279 It was first isolated as a source of disease in 1976. The capsule, made of polysaccharides, is thought to protect against phagocytosis. The observed association of the infection with liver disease (associated with increased serum iron) might be due to the capability of more virulent strains to capture iron bound to transferrin. Toxin production plays a relevant role in pathogenicity.
Signs and symptoms
V. 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, explosive 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 fish such as tilapia or stingrays. These patients may develop a blistering dermatitis sometimes mistaken for pemphigus or pemphigoid.
- Invasive septicemia 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.
V. vulnificus wound infections have a mortality rate around 25%. In patients in whom the infection worsens into septicemia, typically following ingestion, the mortality rate rises to 50%. The majority of these patients die within the first 48 hours of infection. The optimal treatment is not known, but, in one retrospective study of 93 patients in Taiwan, use of a third-generation cephalosporin and a tetracycline (e.g., ceftriaxone and doxycycline, respectively) were associated with an improved outcome. Prospective clinical trials are needed to confirm this finding, but in vitro data support the supposition this combination is synergistic against V. vulnificus. Likewise, the American Medical Association and the Centers for Disease Control and Prevention (CDC) recommend treating the patient with a quinolone or intravenous doxycycline with ceftazidime. The first successful documented treatment of fulminant V. vulnificus sepsis was in 1995. Treatment was Fortaz and intravenous (IV) Cipro and IV doxycycline, which proved successful. Prevention of secondary infections from respiratory failure and acute renal failure are crucial. Key to the diagnosis and treatment was early recognition of bullae in an immunocompromised patient with liver cirrhosis and oyster ingestion within the previous 48 hours, and request by the physician for STAT Gram staining and blood cultures for V. vulnificus.
V. vulnificus is commonly found in the Gulf of Mexico, where more than a dozen people have died from the infection since 1990. Most deaths at that time were occurring due to fulminant sepsis either in the area of oyster harvest and ingestion or in tourists returning home. Lack of disease recognition and the risk factors, presentation, and cause were and are major obstacles to good outcome and recovery.
After the successful treatment of the first patient, the Florida Department of Health was able to trace the origin of the outbreak to Apalachicola Bay oysters and their harvesting in water prone to excessive growth of the organism due to warmth of the water and lack of freshwater dilution by reduced flow of the Chattahoochee River into the Apalachicola River into Apalachicola Bay. A similar situation occurred after Hurricane Katrina in New Orleans.
Patients especially vulnerable are those with liver disease (especially cirrhosis and hepatitis) or immunocompromised states (cancer, bone marrow suppression, HIV, diabetes, etc.). With these cases, V. vulnificus usually enters the bloodstream, where it may cause fever and chills, septic shock (with sharply decreased blood pressure), and blistering skin lesions. About half of those who contract blood infections die.
V. vulnificus infections also disproportionately affect males; 85% of those developing endotoxic shock from the bacteria are male. Females having had an oophorectomy experienced increased mortality rates, as estrogen has been shown experimentally to have a protective effect against V. vulnificus.
The pathogen was first isolated in 1976 from a series of blood culture samples submitted to the CDC in Atlanta. It was described as a "lactose-positive vibrio". It was subsequently given the name Beneckea vulnifica, and finally Vibrio vulnificus by Farmer in 1979.
Increasing seasonal temperatures and decreasing coastal salinity levels seem to favor a greater concentration of Vibrio within filter-feeding shellfish of the US Atlantic seaboard and the Gulf of Mexico, especially oysters (Crassostrea virginica). Scientists have frequently demonstrated the presence of V. vulnificus in the gut of oysters and other shellfish and in the intestines of fish that inhabit oyster reefs. The vast majority of people who develop sepsis from V. vulnificus became ill after they ate raw oysters, most of these cases have been men.
On Thursday, June 18, 2015, an online news story article, featured on the MSN News webpage, and written by Katy Galimberti, an AccuWeather.com staff writer, with commentary provided by AccuWeather meteorologist Alex Sosnowski, stated that eight cases of Vibrio vulnificus infection "have been reported so far in 2015 across six different counties. Two cases resulted in death – one in Brevard County, Florida and one in Marion County, Florida." Mr. Sosnowski then noted that Florida had had warm months previously, and the story said that the pathogen prefers brackish warm water around the Gulf Coastal area. With two deaths out of eight known cases, that localized outbreak would thus far have a fatality (mortality) rate of 25%, higher than many other pathogens, but still lower than many others with even higher fatality rates. Much of the mortality due to V. vulnificus occurs in those patients who develop generalized infections, and in turn develop sepsis or septic shock; many, but certainly not all, of those cases are in compromised individuals.
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