Researchers have long considered tuberculosis, a bacterial respiratorydisease that kills 3 million people each year, a relatively recenthuman 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 oftuberculosis," says Veronique Vincent, senior author of the study andresearcher at Institut Pasteur, Paris, France. These results may haveimportant future implications for improving diagnosis and treatment ofthe disease.
Most tuberculosis cases are caused by Mycobacterium tuberculosis andits close relatives. However, some tuberculosis patients from EastAfrica are infected with unusual bacterial strains that form coloniesthat appear physically different from M. tuberculosis. Using geneticdata from the different strains, Vincent and her colleagues discoveredthat the ancestors of these bacterial strains were also the progenitorsof M. tuberculosis.
These results suggest that M. tuberculosis and related strains recentlyemerged from a much more ancient bacterial species than previouslythought, 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 expansionto the rest of the world may have coincided with the waves of humanmigration out of Africa.
Citation: Gutierrez MC, Brisse S, Brosch R, Fabre M, Omaýs B, et al.(2005) Ancient origin and gene mosaicism of the progenitor ofMycobacterium tuberculosis. PLoS Pathog 1(1): e5.
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