Cholera Gives Up Its Secrets In Mice

Cholera still sickens about 300,000 people every year, mostly in developed countries with poor water treatment systems. Efforts to create a vaccine for the disease have been always been stymied. But results from a cholera model in mice appears to offer a clue as to why that is so.

Researchers at Tufts University infected one group of mice with a cultured strain of the cholera bacteria and a second group of mice with a strain of the bacteria taken from the feces of cholera patients.

The strain taken from patients was as much as 700 times more infectious than the cultured strain. Moreover, when the patient strain was placed in a culture, within 18 hours it reverted to the relatively low-infectious version.

The implication is that the cholera bacteria has evolved a behavior usually seen in complex parasites such as malaria that use different forms for transmission between individuals than they have for infecting individuals once they are in the body (cholera has two chromosomes where most bacteria only have a single chromosome which may play a role in the transformation it makes once inside its hosts).

Since vaccines for cholera have focused on causing an immune response to the cultured form of the bacteria, they likely have failed to cause an immune response to the infectious form of the bacteria.

If the results in mice also hold for human beings, then researchers might be able to finally create an effective vaccine by targeting the proteins of the infectious form of the disease.

Source:

Cholera needs guts to survive. Tom Clarke, Nature, June 6, 2002.

Cholera bacterium’s quick change revealed. Deborah MacKenzie, New Scientist, June 2, 2002.

Leave a Reply