A mouse model shows that low-dose penicillin treatment early in life has lasting effects on gut microbiota, brain physiology and social behaviour. The study, published in Nature Communications, also shows that co-administration of a probiotic - a bacterium that may confer certain health benefits - prevents some of these alterations.

There is increasing evidence that antibiotics, when used early in life, may have unwanted long-term effects, and animal studies have shown that high doses of antibiotics induce long-term effects on behaviour and brain neurochemistry.

John Bienenstock, Sophie Leclercq and colleagues tested whether similar effects could be seen in mice when given a low dose of penicillin during the perinatal period (one week before birth) until weaning (three weeks after birth). The authors found that administering penicillin led to changes in gut microbiota composition, reinforcement of blood-brain barrier integrity, and increased levels of certain brain cytokines (molecules that regulate the immune response). The same alterations were observed in the mice at six weeks of age. In addition, the penicillin treatment led to reduced social behaviour in adult mice, and decreased anxiety-like behaviour and increased aggression in adult male mice. Administration of penicillin with a probiotic (Lactobacillus rhamnosus JB-1) partially prevented some of these alterations.

The authors note that because of the small sample size in some of the analyses, the probiotic’s preventive effects should be validated in further research. Nevertheless, the findings warrant further studies on the potential role of early-life antibiotic use in the development of neuropsychiatric disorders, and the possible attenuation of these by probiotics.