STANFORD, Calif. - Taking advantage of the open-air laboratory that is San Francisco, Peter Small, MD, has collected samples of virtually every case of tuberculosis that has occurred in the city for the last 13 years - almost 3,000 total. In this week's advance online edition of The Proceedings of the National Academy of Sciences, the associate professor of infectious diseases and geographic medicine at the Stanford University School of Medicine and his colleagues present a genetic analysis of 100 of these samples. The findings suggest ways the bacteria can escape a host's immune system or develop antibiotic resistance.

The team took its analysis a step further in a second paper, which appears in the same edition of the journal. They found that people from different regions of the world carry different strains of the tuberculosis bacteria, pointing out the importance of sociological interactions in infectious disease transmission. This also raises the possibility that the pathogen evolves within a geographic population group and doesn't spread to other groups.

"It was remarkable how well the genetics mapped to global geography," said Small. "Co-evolution is highly speculative, but it's an intriguing possibility. Most importantly, it's a hypotheses we now have the technology to address."

Tuberculosis causes more adult deaths than any other infectious disease. Worldwide, one person in three is infected, but it remains a problem primarily in the developing world. However, the emergence of tuberculosis strains resistant to multiple drugs in industrialized countries is prompting renewed interest in vaccination.

There has long been anecdotal evidence that tuberculosis bacteria differ throughout the world, said Small, who is currently on leave from Stanford serving as a senior program officer in the Global Health Program of the Bill and Melinda Gates Foundation. Additionally, he said, studies testing tuberculosis vaccines have varied widely
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Contact: Mitzi Baker
650-725-2106
Stanford University Medical Center
15-Mar-2004

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