Friday, May 13, 2011

Cholera outbreaks in Hyderabad: Altered El Tor strain is the culprit

By Syed Akbar
Hyderabad, May 10: The germ that has been causing regular outbreaks of cholera in Hyderabad is a new mutant of cholera bacterium, and if it is not checked it will further spread in the environment posing severe health threat to people.
A team of researchers from Defence Research and Development Establishment, Gwalior, collected contaminated water samples from Hyderabad and subjected them to bacteriological analysis. The results showed that the regular outbreaks of cholera in twin cities is caused by altered El Tor bacteria.
El Tor bacteria is a new strain that has evolved from the classic cholera bacteria, Vibrio cholerae. This El Tor bacteria has further changed its character to become altered El Tor bacteria. Though altered El Tor bacteria has been isolated in Hyderabad, it is present in other places too.
What causes concern to health planners and medical researchers is that altered El Tor bacteria is adaptive to environment as well as toxigenic in nature. Normal or classic cholera bacteria (Vibrio cholerae) is toxigenic but does not survive in atmosphere for long, while the normal El Tor bacteria is not toxigenic but survives in environment. In contrast, the altered El Tor bacteria - isolated in Hyderabad - has both the properties 
i.e toxic and adaptive to environment.
"Outbreak due to such bacteria should be controlled well in time to prevent further spread in the environment," warns Dr AK Goel of Defence Research and Development Establishment.
"In Hyderabad study, cholera El Tor bacteria with classical strains were reported. This shows that now bacteria are more toxigenic and more adaptive to environment. However, such bacteria have been reported from different parts of country. This shows how bacteria compete in the environment for better evolution," he told this correspondent.
Dr Goel, however, clarified that the altered El Tor biotype has nothing to do with NDM-1 or drug resistance. The world has faced seven cholera pandemics affecting million and millions of people. Initial six pandemics were caused by a Vibrio cholerae strain, which belonged to classical biotype. Classical strains are more toxigenic but less adaptive to environment.
Subsequently, in seventh pandemic, the classical strains were replaced by El Tor biotype strains, which are less toxigenic but more adaptive to environment. In the new millennium, the bacterium again started modifying itself to attain the features of both biotypes. This new germ is responsible for cholera outbreaks in Haiti late last year.

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