In recent years there has been a significant global increase in the prevalence of childhood neurodevelopmental disorders, such as autism and ADHD. Though there are many explanations as to why this could be, such as; genetics, better surveillance and higher quality of healthcare, we can’t ignore how environmental factors also play a role. An environmental factor that is global and relatively recent is the use of antibiotics. Therefore researchers at Rutgers University carried a study on baby mice to determine the effect of penicillin, a common antibiotic on the gut. There is a huge interest in the gut-brain axis, as the gut is important in the health of the brain. Therefore changes made to the gut microbiome such as antibiotics at a young age, could have negative effects on the brain and cause an increase in the prevalence of neurodevelopmental disorders later down the line.
Pregnant mice were separated into three different experimental groups. One third of the baby mice were given low doses of penicillin from the last week of pregnancy till 10 days after their birth. One third of the baby mice were given penicillin from the day they were born till 10 days after their birth. The last set of baby mice were not given any antibiotics, they served as a control. The mice were given the antibiotic through their mother’s milk to reduce the amount of handling which could cause trauma for the mice and introduce bias into this study. RNA was isolated from the frontal cortex and amygdala of these mice. This allowed genes from these parts of the brain to be separated to find the difference between the different groups of baby mice. Additionally the contents of the cecum, colon and small intestines were collected and rRNA was isolated and analyzed. This allowed the difference in the diversity of the bacteria in the microbiome to be identified and analysed.
The results showed that when the baby mice were exposed to low doses of penicillin within the first 10 days of their life, it did affect their microbiome structure and composition. The researchers saw a reduction in the levels of a colonising bacterial species in the intestinal microbiome. The reduction of this species was higher in the baby mice that had been fed low doses of penicillin from the womb in comparison to the baby mice that had been fed low doses of penicillin from birth till 10 days postpartum and the control group of mice. This study also revealed to the researchers that there was a change in the gene produced by the amygdala and the frontal cortex, some genes were differentially up-regulated and down-regulated in the group with antibiotics in comparison with the control group.
This study has provided evidence that early life exposure to antibiotics may have a negative impact on the microbiome and with gene expression within critical brain structures (the amygdala and the frontal cortex), in baby mice. The results suggest that maybe early antibiotic exposure should be strongly evaluated before prescribing. This study is not only of help to healthcare professionals but may also be useful to parents. Though we do have to remember this study was carried out in mice and therefore the representation of this study in newborn infants may be different.
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