Fundamental Food Microbiology, Third Edition - Fuad Fathir

FOODBORNE TOXICOINFECTIONS 399
C. Habitat
Cholera is a human disease. The disease results from the ingestion of infective doses
of Vib. cholerae cells through food and water contaminated with feces of humans
suffering from the disease. Chronic carriers are rare and may not be important in
large epidemics. Marine environments may serve as long-term reservoirs. Both
serotypes, especially non-01, have been isolated from water in the U.S. Gulf Coast
states (Florida, Louisiana, and Texas), in Chesapeake Bay, and along California
coasts. Seafoods (crab, oysters, and finfish) harvested from these areas can carry
contamination and provide the infective dose. Contaminated water can also be the
source of the disease.
D. Toxins and Toxin Production
The toxin of the 01 serotype is a heat-labile, 85-kDa cytotoxic protein with two
functional units. 9 The active A subunit stimulates adenyl cyclase in the intestinal
epithelial cells, causing massive secretion of water along with chloride, potassium,
and bicarbonate in the lining of the intestine. The non-01 serotype produces a
cytotoxin and a hemolysin. Following ingestion of Vib. cholerae cells in sufficient
numbers, the cells colonize the small intestine and multiply rapidly and produce
toxins. When the cells die and lyse, the toxins are released into the intestine.
E. Disease and Symptoms
Vib. cholerae is not contagious. A person must consume a large number of viable
cells through contaminated food or water to contract the disease. Fecal–oral infection
is also possible. The infective dose for cholera is ca. 10 6 viable cells per person, but
it varies with age and health. The incubation period ranges from 1 to 5 d, but is
usually 2 d. The symptoms include the sudden onset of profuse watery diarrhea and
vomiting. Loss of fluid results in dehydration. Other symptoms in severe cases are
painful muscle cramps and clouded mental status. Many infected persons may not
have any symptom or have mild to moderate diarrhea. Treatments consist of rapid
replacement of fluids, along with electrolytes, and administration of proper antibiotics.
In addition to diarrhea, the non-01 toxins also cause infection of soft tissues
and septicemia.
F. Food Association
Food can serve as a source of Vib. cholerae if it is contaminated directly with human
feces from the patient or previously contaminated water. The handling of food by a
person suffering from the disease can also contaminate food, because of poor personal
hygiene. In addition, food originating from natural reservoirs of the causative
bacteria can be contaminated and spread cholera. The natural reservoirs include
marine and brackish water environments. Testing of samples of water, oysters, crabs,
and shrimp from U.S. coastal states has indicated the presence of both 01 and non-
01 serotypes. Table 26.3 lists the types of contaminated foods involved in the disease.
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