We are not alone: the human body is home to trillions of bacteria. At Salk, we are exploring how this community of bacteria helps us stay healthy, and how we might help it fight disease.

‘Superhero’ microbiome bacteria protect against deadly symptoms during infection

As concerns over deadly antibiotic-resistant strains of ‘superbug’ bacteria grow, Janelle Ayres and colleagues are offering a possible solution to the problem: ‘superhero’ bacteria that live in the gut and move to other parts of the body to alleviate life threatening side effects caused by infections.

In a paper published October 30, 2015 in Science, Ayres’ lab reported finding a strain of microbiome Escherichia coli bacteria in mice capable of improving the animals’ tolerance to infections of the lungs and intestines by preventing wasting—a potentially deadly loss of muscle tissue that occurs in serious infections. If a similarly protective strain is found in humans, it could offer a new avenue for countering muscle wasting, which afflicts patients suffering from sepsis and hospital acquired infections (many of which are now antibiotic resistant).

The Salk team identified a population of laboratory mice that appeared resistant to muscle wasting. By comparing the makeup of the intestinal microbiomes of these mice to mice that lacked resistance, the team identified a strain of E. coli that was present only in the wasting-resistant mice. When normal mice were given an oral treatment of this beneficial E. coli strain, they gained the ability to maintain their muscle and fat mass during intestinal infections and pneumonia.

Collaborating with the laboratory of Ronald Evans, the scientists discovered that during an infection by the pathological bacteria, the E. coli left the gut and moved into the fat tissues to induce protective responses that nourish the muscles. Normally, mice with lung and intestinal infections see a drop in a hormone known as insulin like growth factor 1 (IGF-1), a molecule that signals the body to retain muscle mass. But the protective E. coli activated the IGF-1 pathway in the fat tissues, preserving normal IGF-1 levels and maintaining the animal’s muscle in spite of the pathogenic infections. The team will investigate how long this E. coli strain can hold off the pathogens; whether the body’s immune system will eventually eradicate the harmful bacteria completely; and if such a microbe exists in humans.

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