The extensively drug resistant strain of Mycobacterium tuberculosis was linked with more than 50 deaths in a recent outbreak in South Africa.

Genomes of multi-drug-resistant and drug-sensitive isolates were also decoded and initial comparisons revealed the microbes differ at only a few dozen locations along the 4-million-letter DNA code.

Massachusetts Institute of Technology Associate Professor Megan Murray, one of the study's principal investigators, said researchers announced the genome sequence and their initial analysis far in advance of submitting a scientific paper, hoping to accelerate work on drug-resistant TB.

The draft sequences of the various strains each cover roughly 95 percent of the M. tuberculosis genome. Comparing DNA sequences in those regions allows researchers to pinpoint key differences, shedding light on genetic factors that contribute to TB drug resistance.

"These results also lay the groundwork for the development of a rapid diagnostic test for TB," said Murray. "Such a test would enable more rapid and accurate diagnoses, and help to prevent the spread of TB -- especially the most virulent strains."