Drug-resistant tuberculosis can apread as easily as drug-sensitive tuberculosis, study says

Aug 11 2009

New research has found that drug-resistant strains of tuberculosis are just as likely to be transmitted between people as drug-sensitive TB, which could make drug-resistant forms of the disease "highly prevalent in the next few decades," the Australian Associated Press/Sydney Morning Herald reports (Rose, 8/11).

For the study, which was published Tuesday in the Proceedings of the National Academy of Sciences, scientists used genetic data from previous studies to create a model of the way TB progresses. Researchers found that the growth rate, known as "reproductive fitness," of drug-resistant TB is comparable to drug-sensitive TB, according to Australia's ABC News (Phillips, 8/11). "Earlier laboratory work had suggested that despite causing longer lasting infections, the strains did not transmit easily," the Press Association writes (8/11). According to a University of New South Wales press release, the researchers examined strains isolated from Cuba, Estonia and Venezuela. "The finding may reflect an inconsistency in drug treatment programs in these countries," according to the release (8/10).  

The study also found that most resistance today is not a direct result of treatment failure but a result of transmission of the disease from initial treatment failure, ABC News reports. "We found 99 percent of cases are due to transmission from somebody else who had a resistant strain," said Andrew Francis, one of the study researchers from the University of Western Sydney (8/11).

The findings "suggest that limiting further transmission of TB might be an effective approach to reducing the impact of drug resistance," said the University of New South Wales' Fabio Luciani, who led the research, writes the AAP/Sydney Morning Herald (8/11).

In related news, Global Fund To Fight AIDS, Tuberculosis and Malaria Executive Director Michel Kazatchkine on Monday said that multi-drug resistant TB is underdiagnosed around the world and that only a fraction of those who are diagnosed are being treated, Reuters reports. "The Global Fund is funding about 25,000 to 30,000 patients but the estimated total number of cases is 500,000," Kazatchkine said at the 9th International Congress on AIDS in Asia-Pacific, which is being held in Bali, Indonesia.

It costs about $7,000 per year to treat someone who has MDR-TB, which is about 100 times the cost of treating drug-sensitive TB, he said, adding that "there was still an urgency to allocate more money" for MDR-TB. "If we can do it for H1N1, we can do it for TB. These epidemics have been at (pandemic) level 6 plus plus plus plus for years," Kazatchkine said (Lyn, 8/10).