Tuberculosis
Ancient origins of tuberculosis-causing bacteria
By PLoS Pathogens
Aug 19, 2005 - 1:35:00 PM

Researchers have long considered tuberculosis, a bacterial respiratory disease that kills 3 million people each year, a relatively recent human affliction. But a new study in PLoS Pathogens suggests that the disease and the pathogens responsible are much older than previously thought.

"Our results change the current paradigm of the recent origin of tuberculosis," says Veronique Vincent, senior author of the study and researcher at Institut Pasteur, Paris, France. These results may have important future implications for improving diagnosis and treatment of the disease.

Most tuberculosis cases are caused by Mycobacterium tuberculosis and its close relatives. However, some tuberculosis patients from East Africa are infected with unusual bacterial strains that form colonies that appear physically different from M. tuberculosis. Using genetic data from the different strains, Vincent and her colleagues discovered that the ancestors of these bacterial strains were also the progenitors of M. tuberculosis.

These results suggest that M. tuberculosis and related strains recently emerged from a much more ancient bacterial species than previously thought, possibly as old as 3 million years, Vincent says. "Tuberculosis could thus be much older than the plague, typhoid fever, or malaria, and might have affected early hominids," and its expansion to the rest of the world may have coincided with the waves of human migration out of Africa.

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