by Leah Eisenstadt, Broad Institute of MIT and Harvard
In the early 1900s, a cook named Mary Mallon, better known as "Typhoid Mary," spread Salmonella Typhi, the causative agent of typhoid fever, to dozens of her patrons even though she showed no symptoms. Many people today harbor pathogenic Salmonella bacteria for years without feeling sick, making them potential sources of new infections.
A new study by scientists at the Broad Institute of MIT and Harvard, along with colleagues at Tel Aviv University and the Sheba Medical Center in Israel, sheds light on the biological mechanisms that enable another kind of Salmonella to evade the immune system and cause long-term infections.
The team focused on the "nontyphoidal" forms of Salmonella, which cause foodborne illness and, like the typhoidal form, can linger in the body long after the initial infection. By examining the genomes of bacteria collected from hundreds of people with persistent Salmonella infections, they discovered genetic mutations that both reduce the bacteria's "virulence," or ability to infect, and dampen the host's immune responses, creating a kind of molecular camouflage that shields the bacteria from the immune system's gaze.
This insight could one day lead to new diagnostic approaches or treatments that prevent these infections from becoming chronic. The work appears in Cell Host & Microbe.
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