Study in India confirms increase in drug-resistant cholera

Researchers in India have isolated strains of the bacteria that cause cholera which are resistant to some commonly used antibiotics, according to a new study published recently in the Journal of the Indian Medical Association. The researchers said that overuse of certain antibiotics may have contributed to development of the resistant strains and suggest that the use of certain key drugs be reduced to avoid progression and propagation of the resistant strains.

A recent outbreak of severe diarrhoea in West Bengal was already linked with the emergence of strains resistant to furazolidone, an antibiotic commonly used to treat cholera in children. In the latest study, a team from the National Institute of Cholera and Enteric Diseases in Calcutta analysed samples taken from 23 adults stricken with cholera during an outbreak in West Bengal in 1997. Bacteria isolated from the samples were all resistant to five commonly used antibiotics.

Resistance to one of the antibiotics, furazolidone, is particularly worrying, the researchers said. The antibiotic is the first choice drug for children who typically cannot tolerate more powerful antibiotics, such as tetracycline, because of side effects.

Diarrhoea due to cholera infection comes on suddenly but can take as long as five days to develop. Victims suffer from abdominal cramps, nausea, vomiting, dehydration, and, in severe cases, shock. The bacteria thrive in estuaries, lakes, rivers and coastal areas and are associated with blooms of zooplankton, especially copepods, which resemble tiny shrimp. The disease has been a particular concern for health authorities in India following recent widespread flooding in some districts.

Doctors have been warning for years that bacteria are becoming resistant to even the most potent antibiotics. Bacteria become resistant when microbes with a slight tendency to resist an antibiotic survive and pass on their genes; fully resistant bacteria eventually evolve. If a patient fails to take a full course of drugs to eliminate a particular infectious agent, resistance develops even more quickly.

Earlier this year, a team of scientists announced that they had sequenced the entire genome of Vibrio cholerae. In the long term, scientists hope to use the sequence information to identify and remove genes associated with the disease which should facilitate the development of a safe and effective vaccine.

Scott Gottlieb, New York

World Health Organization Genebra - Genebra - Switzerland
E-mail: bulletin@who.int