Test for Detection of Cholera Toxin

Over the past 200 years, there have been at least seven cholera pandemics, of which the latest still continues. A new strain surfaced in 1992, later identified as V cholerae serogroup O139. The outbreaks caused by this new strain may be the beginning of the eighth cholera pandemic. The movement of large groups of people in Monrovia, Liberia, has caused thousands to become infected since June 2003. By mid-September 2003, more than 2,000 new cases were being reported each week.

The cholera enterotoxin produced by V cholerae serogroups O1 and O139 causes an increase in cAMP within the cells of the gastrointestinal tract, which results in the secretion of water and electrolytes. The disease is threatening but can easily be treated, although 75% of cases are asymptomatic. Diagnosis is confirmed by the isolation of V cholerae O1 or O139 from stool culture. Isolates should be serotyped and they can also be tested for toxin production. However, existing serologic methods may not be able to detect a new serogroup. The detection of cholera toxin is an important indicator of virulence.

Reversed passive latex agglutination (RPLA) toxin detection kits are now available from Oxoid (Basingstoke, UK). These give clear, easy-to-read results in less than 24 hours, which is faster than other methods. Latex particles are sensitized with antibodies to the target toxin. In the presence of that toxin, the latex particles agglutinate to form a clearly visible lattice structure. In addition to detecting V cholerae enterotoxin, the test will detect Escherichia coli heat-labile enterotoxin.

Oxoid also offers tests for staphylococcal enterotoxins A, B, D, and D, Bacillus cereus enterotoxin, E coli verotoxins, staphylococcal toxic shock syndrome toxin, and Clostridium perfringens type A enterotoxin.




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