Manipulating bacteria in the stomach may help protect against stroke. Researchers from Cornell University have discovered a new way to decrease stroke severity by manipulating the immune system using gut bacteria.

New research reveals that mice treated with a combination of antibiotics experienced ischemic strokes that were 60 percent less severe than those that weren't given antibiotics. Researchers said the latest findings suggest that gut bacteria can leverage the immune system to lower the severity of stroke.

Researchers noted that ischemic strokes are the most common type of stroke in which an obstructed blood vessel stops blood from reaching the brain.

"Our experiment shows a new relationship between the brain and the intestine," said Dr. Josef Anrather, an associate professor of neuroscience in the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine. "The intestinal microbiota shape stroke outcome, which will impact how the medical community views stroke and defines stroke risk."

Researchers said experimental results suggest that changing the bacterial community in the gut can help prevent stroke. While more research is needed to understand the mechanism behind the stroke-mitigating effects of gut bacteria, Anrather and his team noted that the study revealed that bacteria did not directly interact with the brain to lower stroke severity. Instead, gut bacteria seemed to have increased neural survival by changing the behavior or immune cells that traveled to the brain's meninges to relieve the effects of the stroke.

"Commensal gut bacteria impact the host immune system and can influence disease processes in several organs, including the brain. However, it remains unclear whether the microbiota has an impact on the outcome of acute brain injury. Here we show that antibiotic-induced alterations in the intestinal flora reduce ischemic brain injury in mice," researchers wrote in the study.

"One of the most surprising findings was that the immune system made strokes smaller by orchestrating the response from outside the brain, like a conductor who doesn't play an instrument himself but instructs the others, which ultimately creates music," said Dr. Costantino Iadecola.

Researchers said the latest findings suggest that changing dietary habits may also help prevent or reduce the severity of stroke.

"Dietary intervention is much easier to accomplish than drug use, and it could reach a broad base," Anrather concluded. "This is a little far off from the current study - it's music of the future. But diet has the biggest effect of composition of microbiota, and once beneficial and deleterious species are identified, we can address them with dietary intervention."

The findings are published in the journal Nature Medicine.