Cholera

How the cholera bacterium causes disease

The main symptoms of cholera are diarrhoea and consequently dehydration. Some people infected with the cholera bacterium show few, if any, symptoms. Some act as carriers, unwittingly spreading the disease.

Vibrio cholerae is transmitted by the ingestion of water or food that has been contaminated with faecal material containing this pathogen. Once ingested, it causes symptoms of the disease in the following ways:

·         Almost all of the bacteria ingested by humans are killed by the acidic conditions in the stomach. However, a few may survive, especially if the pH is above 4.5.

·         When the surviving bacteria reach the small intestine they use their flagella to propel themselves in a corkscrew-like fashion through the mucus lining of the intestinal wall.

·         They then start to produce a toxic protein. This protein has two parts. One part binds to specific carbohydrate receptors on the cell-surface membrane. As only the epithelial cells of the small intestine have…