In a landmark study, researchers have found that providing clinical (low) doses of penicillin to pregnant mice and their offspring results in long-term behavioral changes.

Penicillin has lasting effects in both sexes on gut microbiota, increases cytokine expression in frontal cortex, modifies blood–brain barrier integrity and alters behavior.  These changes include elevated levels of aggression and lower levels of anxiety, accompanied by characteristic neurochemical changes in the brain. Giving these mice a lactobacillus strain of bacteria helped to prevent these effects. The study was published in Nature Communications.

Other studies have shown that large doses of broad-spectrum antibiotics in adult animals can affect behavior. But there haven't been previous studies that have tested the effects of clinical doses of a commonly-used, narrow-spectrum antibiotic such as penicillin on gut bacteria and behavior.

"There are almost no babies in North America that haven't received a course of antibiotics in their first year of life," says the senior author. "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 as yet unborn children or children after birth, this raises further questions about the long-term effects of our society's consumption of antibiotics."

A previous study in 2014 raised similar concerns after finding that giving clinical doses of penicillin to mice in late pregnancy and early life led to a state of vulnerability to dietary induction of obesity.

The research team will follow up their studies by analyzing the effects of penicillin on the offspring, if given only to the pregnant mothers. They also plan on investigating the efficacy of different types of potentially-beneficial bacteria in protecting offspring against the behavioral changes that result from antibiotic usage.

http://www.nature.com/articles/ncomms15062