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Vibrio vulnificus (page 1)
(This chapter has 3 pages)
© Kenneth Todar, PhD
Vibrio vulnificus is
recognized by many microbiologists, less so by the public. Yet, in
country, the bacterium causes a disease with over a 50 percent
rate, and it causes 95 percent of all seafood-related deaths.
Vibrio vulnificus is a Gram-negative, motile
bacterium found in marine and estuarine environments. It has been
from seawater, sediments, plankton and shellfish (oysters, clams and
located in the Gulf of Mexico, the Atlantic Coast as far north as Cape
Cod, and the entire U.S. West Coast. The bacterium thrives in warm
and is part of a group of vibrios that are "moderate halophiles",
meaning they require salt for growth. Vibrios are frequently
from oysters and other shellfish in warm coastal waters during the
months. This correlates with the peak incidence of disease caused by the
Vibrio vulnificus is a Gamma Proteobacterium in the Family Vibrionaceae,
with two other human pathogens Vibrio cholerae, the agent of
epidemic cholera, and Vibrio parahaemolyticus, which causes
acute diarrhea. Vibrios are one of the most common organisms in surface
waters of the
They occur in both marine and freshwater habitats and in associations
aquatic animals. Some species are bioluminescent and live in
associations with fish and other marine life. Other species are
for fish, eels, and frogs, as well as other vertebrates and
V. cholerae and V. parahaemolyticus are pathogens of
Both produce diarrhea, but in ways that are entirely different. V.
is an invasive organism affecting primarily the colon; V. cholerae
is noninvasive, affecting the small intestine through secretion of an
Vibrio vulnificus is an emerging pathogen of humans. It
wound infections, gastroenteritis, or a syndrome known as primary
It was first recognized as an agent of disease in 1976. The first
documented case of disease caused by the bacterium was in 1979.
Figure 1. Vibrio
a typical marine vibrio - a slightly curved bacterium, motile by means
of a single polar flagellum.
V. vulnificus causes disease in individuals who eat
seafood (usually raw or undercooked oysters) or have an open wound that
is exposed to seawater. Among healthy people, ingestion of V.
cause vomiting, diarrhea, and abdominal pain. Most V.
infections are acute and have no long-term consequences.
In immunocompromised persons, particularly those with chronic liver
disease, V. vulnificus can invade the bloodstream from either a
wound or from the GI tract, causing a severe and life-threatening
called primary septicemia, characterized by fever, chills, septic shock
and death. Blistering skin lesions accompany the disease in about 70%
the cases. V. vulnificus bloodstream infections are fatal about
50% of the time.
Although V. vulnificus is a rare cause of disease, it
likely that it is unrecognized and underreported (one estimate of the
number of cases annually in the U.S. is as high as 45,000). Between
and 1995, CDC received reports of over 300 V. vulnificus
from the Gulf Coast states, where the majority of cases occur.
Persons who are immunocompromised, especially those with chronic
disease, are at risk for V. vulnificus when they eat raw
particularly oysters. These individuals are 80-200 times more
to develop V. vulnificus primary septicemia than are healthy
For this particular risk group, the infection carries one of the
mortality rates of all bacterial infections.
Health conditions that place a person at risk for serious illness or
death from V. vulnificus infection include liver disease,
diabetes, stomach problems, kidney disease, cancer, immune disorders
HIV) and long-term steroid use. In these individuals, the
enters the blood stream, resulting in septic shock, rapidly followed by
death in many cases. Such individuals are strongly advised not to
raw or inadequately cooked seafood.