When given in late pregnancy and early life, low-dose penicillin caused long-term behavioral  and microbial changes in laboratory mice, revealed a landmark study conducted at St. Joseph's Hamilton and McMaster University. The research was conducted amid increasing concerns about the long-lasting effects of antibiotics.

"We wanted to see if low dose (clinical pediatric child equivalent) penicillin by mouth given to mice in the last few days of pregnancy and through until weaning had any long term effects in the offspring on the brain and/or behaviour, as well as the bacteria in the gut," Dr. John Bienenstock, Director of the Brain-Body Institute at St. Joseph's Healthcare Hamilton and Distinguished Professor at McMaster University, said to ALN.

The research, published in Nature Communications and funded by the United States Office of Naval Research, showed that mice given this antibiotic displayed elevated levels of aggression as well as lowered anxiety. Neurochemical changes in the brain and an imbalance in their gut microbes also occurred.

Interesting, giving the mice a lactobacillus strain of bacteria seemed to prevent these effects.

This finding occurs as many have grown concerned about the long-term effects of antibiotics. Many infants prescribed antibiotics at a young age. Additionally, antibiotics are increasingly found in the meat and dairy products people consume daily.

"If indeed any of these findings can be translated to the clinical situation, they suggest that we should be careful about really having to take antibiotics in late pregnancy and also be concerned about the consumption of probiotics in childrens' early life," Dr. Bienenstock added.

"Clearly, this is an experimental study in mice and we do not know whether we can extrapolate to humans, however, it does wave a flag of caution which now should encourage the sort of clinical studies mentioned before."