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Ciprofloxacin (top)

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A new study shows that overuse of a drug used to prevent and treat malaria may be contributing to growing resistance to a related antibiotic.

Researchers report in the journal PLoS ONE that Escherichia coli bacteria resistant to the antibiotic ciprofloxacin — a type of fluroquinolone — were detected in the digestive tracts of villagers from remote rainforest communities in Guyana, despite them never having been given the drug.

Most of the villagers had been given the drug chloroquine — a drug closely related to ciprofloxacin — to prevent and treat malaria.

535 villagers were sampled for resistant bacteria in the three-year study, with 4.8 per cent found to be carrying ciprofloxacin-resistant E. coli.

Guyana recorded over 11, 000 cases of malaria last year, the minister of health, Dr Leslie Ramsammy, told SciDev.Net. He said the findings were "interesting" and that the Ministry of Health would commission its own study to test the accuracy of the research results.

The antibiotic ciprofloxacin is used throughout the world to treat bacterial infections, including pneumonia, urinary tract infections and sexually transmitted diseases. This is the first study to show that resistance can emerge in individuals never exposed to the antibiotic.

Drug-resistant bacteria are known to arise from overuse of antibiotics, which is why researchers were surprised to discover that they can develop in areas that do not have access to ciprofloxacin, says study co-author Michael Silverman, an infectious disease specialist at Lakeridge Health Network in Ontario, Canada.

In fact, he says, ciprofloxacin-resistant E. coli were even more widespread in remote Guyanese villages than in United States intensive care units "where every second person is on antibiotics".

"E. coli is one of the most common causes of infection in humans. A decade ago it was nearly universally susceptible to ciprofloxacin," says Andrew Simor, a senior scientist at the Sunnybrook Health Sciences Center at the University of Toronto.

Today, he says, as many as 30 per cent of hospital patients tested have E. coli that fails to respond to ciprofloxacin.

Resistance to ciprofloxacin could be an important public health problem in areas where malaria is endemic — and therefore chloroquine use common — because ciprofloxacin and other fluroquinolones could be less effective, write the authors.

Silverman stressed that the study highlights the need to continue to try to prevent malaria through the use of insecticide-treated bed nets, along with the development of an effective vaccine.

Link to full paper in PLoS ONE