Johns Hopkins researchers have found evidence in mice that a tuberculosis (TB) infection in the lungs triggers immune system signaling to the gut that temporarily decreases the diversity of bacteria in that part of the digestive tract.
The Johns Hopkins researchers showed that this decrease in diversity of gut bacteria as measured in fecal samples happened quickly within six days after mice were exposed to an aerosol mixture of M. tuberculosis, the TB bacteria. This prompt shift in diversity, they say, suggests that the immune system is attacking the gut bacteria, decreasing the overall diversity by causing certain bacteria to outgrow others in the gut.
The finding was also replicated using a different strain of the TB microbe, according to a report on the work in the May 12 issue of the online journal PLOS One.
Study leader Kathryn Winglee, a Ph.D. student working at the Johns Hopkins Center for Tuberculosis Research, says the finding is important, because it could lead to improved diagnosis of TB, a disease that infects one-third of the world's population and in 2010 caused 1.4 million deaths.
"The fact that the bacterial populations change in the gut means that we can begin to use this observation for TB diagnosis," Winglee says. "TB diagnosis is currently challenging, but a simple stool sample test that detects changes in the diversity of gut bacteria after TB infection in the lung might improve diagnosis."
The finding also adds to growing evidence that the various parts of the immune system found in mucous membranes throughout the body interact as a "global" organ rather than work as separate, individual sites of immune function. Mucous membranes are the moist linings of areas of the body exposed to the environment, such as the nostrils, mouth, lungs, genitals and intestinal tract. These membranes form a protective barrier against infection and contain immune system cells.
|Contact: Stephanie Desmon|
Johns Hopkins Medicine