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Dr. John Bienenstock (left) and Dr. Paul Forsythe investigate the effects that gut bacteria have on the brain.

In a landmark study, researchers at St. Joseph’s Healthcare Hamilton have found that providing low doses of penicillin to pregnant mice results in behavioural changes in their offspring – such as elevated levels of aggression and lower levels of anxiety. These changes remained present as the mice reached maturity. Giving these mice a strain of probiotic bacteria called JB-1 helped to reverse and prevent these effects.

The study was published in Nature Communications and was funded by the United States Office of Naval Research.

“There are almost no babies in North America that haven’t received a course of antibiotics in their first year of life,” states Dr. Bienenstock, researcher at St. Joseph’s Healthcare Hamilton and Distinguished University Professor at McMaster University. “Antibiotics aren’t only prescribed, but they’re also found in meat and dairy products. If mothers are passing along the effects of these drugs to their children, this raises the questions about the effects of our society’s consumption of antibiotics.”

Another study led by St. Joe’s researchers has found that the same strain of probiotic bacteria (JB-1) can alleviate symptoms of anxiety and inflammation.

By testing the probiotic bacteria JB-1 in animal models – the research showed that the probiotic was able to protect mice against anxiety, social stress and inflammation caused by changes in the immune system.

“Interestingly, the probiotic only had an effect in mice that showed symptoms of anxiety. Those without anxiety were not affected,” says Dr. Paul Forsythe, the study’s senior author and researcher at St. Joseph’s Healthcare Hamilton and McMaster University. “This suggests that if this probiotic were to act the same way in humans, you wouldn’t expect to see changes in mood or behavior in those without anxiety symptoms.”

This study was also funded by the United States Office of Naval Research.

“The US Navy is interested in this research as it shows promise for improving resistance to chronic stress and potentially preventing PTSD,” says Dr. Forsythe. “As scientists, we’re interested in learning more about the mechanisms that make these probiotics function the way that they do.”


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