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A 'Rugged and Feeble' Bacterium

Leprosy, a disease that may conjure up images of medieval leprosariums, still infects some 200,000 people a year, mostly in developing nations like India and Brazil, the New York Times reports.

Recent analysis of the bacterium behind the disease, Mycobacterium leprae, indicates that it is "rugged and feeble, exacting and inept," the Times' Natalie Angier says,

Though leprosy can now be treated with a course of antibiotics, M. leprae still puzzles researchers. It dies easily outside a host, many people are immune to it, and it has a bulky genome that is nearly half pseudogenes, Angier adds. It also does not grow well in cell culture nor in animals, with the exception of the armadillo.

But a recent comparative genomic analysis found that it's been around for a long time — researchers traced the ancestor of M. leprae and the related M. lepromatosis back some 10 million years to when it infected the ancient hominin ancestor of people.

Other genetic work, she notes, has focused on how some people seem to be more susceptible to M. leprae. There appears, she adds, to be a link between that susceptibility and other immune conditions like Crohn's disease.

"I'm absolutely convinced that leprosy must be thought of as a genetic disease as well as an infectious one," Erwin Schurr, a molecular geneticist at McGill University, tells her.