by Alison Bowler

Created on: August 24, 2010   Last Updated: October 23, 2010

Vibrio cholerae is a highly motile comma shaped gram-negative staining bacterium. It is the causative organism of cholera. The word cholera comes from the Latin and means flow of bile.

People usually catch cholera from the ingestion of contaminated water or food. Direct infection from person to person is rare. To catch the disease from water a person has to ingest between one thousand and a million bacteria. The infectious dose of bacteria in food is lower at about one hundred to ten thousand bacteria.

Most cases of cholera come from Africa, Asia, India and the Middle East. However, it is not a tropical disease. Cholera is endemic in areas of poor hygiene and sewerage provision. It is a common problem in refugee camps. In such camps, safe water supplies and sewage systems are difficult, if not impossible, to maintain. Eating undercooked or raw contaminated shellfish causes in a number of isolated cases of cholera. Recently shellfish from the US Gulf coast has formed a reservoir for infections with V. cholerae O1 El Tor Inaba. USA caught shellfish causes only a few cases of cholera annually. From 1995 to 2000, there were 24 USA caught cases and in 2005, there were four such cases.

Vibrios are sensitive to acid conditions and normal stomach acid will kill smaller numbers of the bacteria before they can enter the intestines. Food protects the bacteria from the acid so a lower infectious dose is required for infection to occur in food associated cases. People taking certain medications, such as antacids, have a lower resistance to infection with cholera. Other persons who have a higher chance of developing the disease are those with chronic gastritis or who have had a gastrectomy.

When the bacteria reach the small intestines, they start to multiply and produce an enterotoxin. The enterotoxin is responsible for the symptoms of cholera. The enterotoxin binds to cells lining the duodenum and upper jejunum. It causes crypt cells to secret chloride and water into the upper intestine. The colon is insensitive to the toxin and continues to absorb water. However, the amount of fluid produced in the upper intestine overwhelms the colon’s ability to absorb water, leading to profuse watery diarrhea.

The incubation period or cholera lasts from a few hours to five days. Most cases of cholera are symptomatic for two to five days. 

A patient suffering from cholera produces extremely watery stools, sometimes, called rice water stools. The diarrhea frequently has a fishy

• 1
• 2
• Next Page >>