Gut bacteria help fight off sepsis in mice

In addition to treating sepsis with antibiotics, doctors may prescribe other treatments, such as surgery to remove damaged tissue. (Gerd Altmann)

Sepsis, a potentially life-threatening complication of infection, is currently treated with antibiotics which kill the infection-causing bacteria. But research out of the University of Pennsylvania spotlights an alternative approach: Delivering certain gut microbes to mice boosted antibody levels in mice, protecting them against the widespread inflammation that can lead to sepsis.

Sepsis occurs when infection-fighting chemicals released into the bloodstream cause an inflammatory response, according to the Mayo Clinic. This inflammation can then trigger a chain reaction throughout the body, which could damage tissues and lead to organ failure.

The Penn team looked into gut microbes because they have been linked to immunoglobulin A (IgA) responses in previous research. Other work has shown that “people with IgA deficiencies are more likely to succumb to sepsis,” according to a statement. This type of antibody is “readily” found in humans and mice, but its role in warding off sepsis was unknown.

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The researchers found that exposing mice to several types of Proteobacteria raised their blood IgA levels. They then transferred blood with elevated IgA to mice with sepsis, observing that these mice survived longer than mice infused with blood lacking IgA.

“Taken together, the findings suggest that commensal microbes can have a substantial impact on IgA levels in the blood, resulting in protection against bacterial sepsis,” the researchers said in the statement. The findings appear in the journal Cell Host & Microbe.

A new treatment for sepsis would be a boon for hospital systems, as one-third of patients who die in hospital have sepsis, and a CDC evaluation found that 7 in 10 sepsis patients “recently used healthcare services or had chronic diseases requiring frequent medical care.” More broadly, of the more than 1.5 million people in the U.S. who get sepsis each year, about 250,000 of them will die.

And that’s not all—an alternative to antibiotics could curb the use of them to fight infections and make a dent in the rise of antibiotic-resistant bacteria.

The Penn researchers, led by first author Joel Wilmore and senior author David Allman, will try to unravel how, exactly, IgA protects the body against sepsis. They will also investigate ways to translate their findings into a treatment that can be used in human disease.