(ORDO NEWS) — Children exposed to antibiotics have an increased risk of developing asthma.
Treating mice with antibiotics for the first few days of their lives irreversibly inhibits the development of their gut bacteria, resulting in altered immune responses to common allergens.
The researchers write in the journal Mucosal Immunology that this discovery provides the first strong evidence for a causal relationship between childhood antibiotic use and the subsequent development of asthma and allergies.
” The takeaway is simple : avoid antibiotics in young children whenever possible because it can raise the risk of serious, long-term allergy and/or asthma problems,” study author Martin Blaser explained in a statement.
In their experiment, the researchers exposed mice to plain water, azithromycin, or amoxicillin for the first nine days of their lives. In their report, the authors explain that they chose these drugs because they are “the two most commonly prescribed antibiotics in pediatric practice.”
By tracking the composition of the animals’ gut bacteria throughout their lives, the researchers found “consistent differences in the gastrointestinal microbiota of antibiotic-treated pups into adulthood.”
Importantly, when rodents were later exposed to house dust mites, those who received antibiotics as infants showed increased production of antibodies and inflammatory cytokines, suggesting an allergic reaction. This effect was especially noticeable in mice that were exposed to azithromycin.
To determine if antibiotics affect young and old animals equally, the researchers then subjected adult mice, which lacked any gut bacteria, to faecal samples taken from pups that had received antibiotics.
The results showed that the immune response of these elderly rodents to common allergens did not differ from that of unexposed mice.
However, pups born to these adult mice “acquired a microbiota that was disrupted by antibiotics at birth,” leading to increased immune responses to dust mites, as well as “altered airway reactivity.”
According to Blaser, these results “provide strong evidence that antibiotics cause unwanted immune responses through their effects on gut bacteria, but only if the gut bacteria are altered in early childhood.”
Previous studies have shown that children with abnormal microbiota at one year of age are more likely to develop asthma by age five.
Until now, the causal mechanism underlying this trend has remained unknown, but the authors say their study “provides evidence for a predisposition to altered microbiome-dependent lung physiology.”
To sum up their findings, the researchers conclude that there is a critical “window in early life” during which a growing microbiome supports healthy immune system development.
Therefore, the use of antibiotics during this period can interrupt this process, potentially causing allergies and asthma later in life.
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