A team of scientists from the New York University Grossman School of Medicine divided the mice into three groups. One group of pregnant mice was exposed to penicillin the week leading up to birth. The second group of mice was exposed to penicillin during the week following birth. The third group of mice, the control group, had no antibiotic exposure.
Low-Dose Penicillin Exposure Disrupts the Microbiome
The scientists found that exposure to even low doses of penicillin changed the composition of the microbiome in the mice. More specifically, the antibiotic-exposed pups had notably decreased numbers of the beneficial bacteria, lactobacillus, among other species of bacteria and notably increased numbers of Enterococcus, Enterobacteriales, and Pseudomonas, among others.The scientists further found that these changes were linked to changes in gene expression in the brains of the exposed mice. Most disturbingly, perhaps, this experiment showed that multiple pathways crucial for normal neurodevelopment were negatively affected in the antibiotic-exposed mice.
Because the doses of penicillin were so low, the researchers argued that it’s unlikely that the brain effects they observed were a direct result of the antibiotics themselves. Instead, they hypothesized that it’s more likely that the brain changes observed in the mice were due to the changes in their microbiomes.
In other words, due to antibiotic exposure, “the gut-brain axis is perturbed leading to organizational effects that permanently alter the structure and function of the brain,” according to the scientists.
“These results provide evidence that early-life antibiotic exposure in humans may have effects not only on the infant microbiome but also on gene expression within critical brain structures, including the frontal cortex and amygdala, which are vulnerable to perinatal insults,” the scientists wrote.
“These initial findings require further validation but suggest a paradigm shift in early-life antibiotic use should be considered. Although not considered a potentially severe CNS [central nervous system] teratogen such as alcohol, cocaine, or toxoplasmosis ... early-life antibiotic use may have unexpected consequences.”
Dr. Robert Zajac, a pediatrician based in Eden Prairie, Minnesota, who wasn’t involved in the study, finds these results to be concerning, but not surprising. Zajac said that he and his medical team try to not use antibiotics unless they’re absolutely necessary.
Exposed Before Birth
For many babies, antibiotic exposure usually begins before birth. In fact, there’s evidence that a large percentage—perhaps as much as one-third—of the 3.75 million babies born in the United States each year are getting dosed with antibiotics before, during, or just after birth.While the 2013 study emphasized the success of the prenatal use of antibiotics to avoid Group B strep infections, which can be dangerous or even deadly for newborns, the data within it suggests that we’re prescribing antibiotics to pregnant women far more often than necessary.
Falsely Assumed Safe
Antibiotic use before or around the time of birth has long been considered to have minimal adverse effects on babies. However, studies that suggest they’re safe have only looked for the most obvious, short-term consequences of antibiotic over-use, such as increased thrush infections (an overgrowth of yeast usually kept in check by a healthy microbiome). These older studies haven’t examined longer-term health consequences.Experts now believe that the communication between the central nervous system and the intrinsic nervous system of the gastrointestinal tract, which has come to be known as the “gut-brain axis,” is crucial not only for proper digestion and proper brain functioning, but also for overall health.
“There’s clear evidence that the gut can have profound effects on the brain, and gut flora is part of that process,” said Dr. Elizabeth Mumper, a pediatrician in private practice in Lynchburg, Virginia, who specializes in brain disorders. “So we know that certain flora in the gut can produce metabolic products that give chemical messages to the brain that can alter feelings, emotions, and potentially alter cognition.”
“We also know that the gut flora that’s developed in the first thousand days of life has a profound impact on the child’s chances of having chronic illness later in life,” Mumper said. “In general, the more diverse gut flora, the less the child is likely to have chronic illness later on, and antibiotics have the effect of killing off some of that good gut flora, therefore leading to less diversity.”
My friend and colleague, Zoey O’Toole, a health advocate with an undergraduate degree in physics who has worked as an electrical engineer and a computer programmer, has long suspected that over-exposure to antibiotics played a role in her children’s speech and neurological issues.
Better Outcomes
In a research study published in 2013 in the North American Journal of Medicine and Science, Mumper herself found a clear association between antibiotic use and autism.Changing Clinical Practice
According to the New York University research, prior to 1945, no children were exposed to antibiotics during childhood. Today, the average U.S. child receives nearly three rounds of antibiotics before the age of 2. If early antibiotic exposure is indeed causing altered brain function in a high percentage of U.S. children, we must find ways to mitigate those effects. “Our present findings should trigger re-examining widespread antibiotic prescriptions when their use is not directly indicated,” the study authors wrote.But, perhaps the most important tactic is a combination of prevention and nutrition.
“It’s really important not to over-medicate kids in the first thousand days of life,” Mumper said. “And also to really work on their nutrition, so [that] when you first start to feed them, they become used to bitter tastes and fermented foods. Sugar is an enemy of healthy gut flora, so it’s important to help your baby develop a palate that won’t just prefer sweet foods.”
