Cholera pathogen Vibrio cholerae can grow in freshwater: epidemiological and immunological consequences
The majority of bacterial species under the Vibrio genus are common flora in brackish waters and estuaries. The causative agent of dysenteric disease cholera, Vibrio cholerae, wasn’t thought to be any different. The disease has always been associated with ingestion of contaminated water and sea food. However, researchers at the Swiss Federal Institute for Aquatic Science and Technology (EAWAG) showed that V. cholerae not only grows but actually thrives in freshwater.
The study focused on the V. cholerae O1 Ogawa El Tor strain, one of the serotypes responsible for the recently reported outbreaks in India. Study results show that the bacterium is actually euryhaline and can grow in a wide range of salinities ranging from brackish to lake waters. A determinant factor for its growth in freshwater is the amount of apparent assimilable organic carbon (AOCapp). V. cholerae produces a toxin that causes the characteristic diarrheal symptoms of the disease.
In another European study, Belgian researchers looked more in detail into the transport mechanisms of the B-protomer subunit of the cholera toxin. According to Vanden Broeck and colleagues (2007), the B-subunit “displays the capacity to fortify immune responses to certain antigens, to act as a carrier and to be competent in inducing immunological tolerance.”These findings have some consequences on the epidemiology and preventive strategies of cholera.
The first study highlights the risks of contamination not only in coastal waters but in inland areas and lakes while the second study indicates a potential use for the cholera toxin in vaccine development.
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