From: Reuters
Published November 20, 2007 01:27 PM

Scientists decode genes of resistant TB

WASHINGTON (Reuters) - Researchers have decoded the gene map of a strain of extensively drug-resistant tuberculosis and said on Tuesday their work has identified mutations that may help develop better treatments.

They also sequenced the genome of another dangerous strain called multidrug-resistant TB, as well as run-of-the-mill tuberculosis bugs, and found a few mutations may explain how the mutant strains evade antibiotics.

"By looking at the genomes of different strains, we can learn how the tuberculosis microbe outwits current drugs and how new drugs might be designed," said Megan Murray of the Broad Institute at the Massachusetts Institute of Technology and Harvard University.

The team at Broad, well known for its genome sequencing work, decided to make its findings public immediately instead of waiting to publish the study in a scientific journal.

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"It is important that genomic data be made immediately available, particularly to researchers in areas most heavily burdened by disease," said Broad's Eric Lander.

Tuberculosis, or TB, is a disease caused by a bacteria called Mycobacterium tuberculosis. It infects up to 2 billion people, one-third of the world's population, although most have latent, or inactive infections.

In 2005, 8.8 million people became infected with TB and 1.6 million died of it. It takes months of careful antibiotic treatment to clear the infection.

The microbe can mutate and now an estimated 500,000 people globally have multidrug-resistant, or MDR TB, according to the World Health Organization. Standard antibiotics do not affect MDR TB, and patients need special drugs.

Extensively drug resistant TB, XDR TB for short, is virtually immune to traditional antibiotics and kills up to 85 percent of those infected.

The researchers studied an XDR TB strain that affected hundreds of people in the KwaZulu-Natal province of South Africa.

"Genetic characterization of this strain is essential for developing tools to get this epidemic under control," said Willem Sturm, of the University of KwaZulu-Natal, who worked on the study.

The researchers also identified some genes that may be important to the spread of TB. They said it was lucky the various strains are so similar genetically.

"These results also lay the groundwork for the development of a rapid diagnostic test for TB," Murray said in a statement.

"Such a test would enable more rapid and accurate diagnoses, and help to prevent the spread of TB -- especially the most virulent strains."

It can take weeks to tell if a person is infected with standard TB or a more dangerous MDR or XDR strain.

The sequences are published on the Internet at http://www.broad.mit.edu/XDR_TB or through the TB database, www.tbdb.org.

(Editing by Will Dunham Doina Chiacu)

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