Early exposure to antibiotics kills healthy bacteria in the digestive tract and can cause asthma and allergies, a new study has found.
The study, published in Mucosal immunologyprovided the strongest evidence to date that the long-standing link between antibiotic exposure in early childhood and the later development of asthma and allergies is causal.
“The practical implication is simple: avoid the use of antibiotics in young children whenever you can, as it may increase the risk of significant, long-term allergy and/or asthma problems,” said lead author Martin Blaser, director of the Center for Advanced Biotechnology. and medicine at Rutgers.
In the study, the researchers, who came from Rutgers, New York University and the University of Zurich, noted that antibiotics, “among the most widely used medications in children, affect gut microbiome communities and metabolic functions. These changes in microbiota structure may impact host immunity.”
In the first part of the experiment, five-day-old mice were given water, azithromycin or amoxicillin. After the mice matured, the researchers exposed them to a common dust mite-derived allergen. Mice that received either antibiotic, especially azithromycin, showed high levels of immune responses, ie allergies.
The second and third parts of the experiment tested the hypothesis that early exposure to antibiotics (but not later exposure) causes allergies and asthma by killing certain healthy gut bacteria that promote healthy immune system development. .
Lead author Timothy Borbet first transferred bacteria-rich fecal samples from the first group of mice to a second group of adult mice without prior exposure to bacteria or germs. Some received samples from mice that received azithromycin or amoxicillin during infancy. Others received normal samples from mice that had been given water.
Mice that received antibiotic-modified samples were no more likely than other mice to develop immune responses to house dust mites, just as people who receive antibiotics as adults are no more likely to develop asthma or allergies than those who do not receive them.
Things were different, however, for the next generation. Offspring of mice that received antibiotic-modified samples reacted to the mites more than those whose parents received non-antibiotic-modified samples, just as mice that were initially given antibiotics as babies reacted more to the allergen than those who received water.
“This was a carefully controlled experiment,” Blaser said. “The only variable in the first part was the exposure to the antibiotics. The only variable in the other two parts was whether the mix of gut bacteria was affected by the antibiotics. Everything else about the mice was the same.
Blaser added that “these experiments provide strong evidence that antibiotics cause the development of undesirable immune responses via their effect on gut bacteria, but only if gut bacteria are altered in early childhood.”