Giving infants antibiotics that also kill many evolving healthy gut bacteria could be putting them at risk of developing asthma, obesity and allergies later on, a groundbreaking Irish study suggests.
Cork-based researchers used advanced DNA sequencing for the first time to identify and count gut flora in newborns.
The composition in the gut of infants treated with broad-spectrum antibiotics was found to be still altered eight weeks after treatment.
While antibiotics have saved many lives, altering gut microbiota very early in life could have a negative effect on development of the immune system, affecting long-term health.
Scientists believe the research makes the case for using more targeted, narrow-spectrum antibiotics to treat infants over the shortest possible time.
It looked at nine infants treated with intravenous ampicillin/gentamicin wi-thin 48 hours of birth over a two-month period.
The babies’ gastrointestinal flora was compared to nine infants who received no antibiotics.
At four weeks, beneficial bacteria, including bifidobacteria and lactobacilli, were significantly reduced in the treated group. Although the numbers bounced back by the study’s end, the species’ diversity did not.
The study was cond-ucted by scientists in the Alimentary Pharmabiotic Centre in University College Cork, Cork University Maternity Hospital, and Teagasc Moorepark Food Research Centre in Fermoy.
"This is the first sequencing-based study to demonstrate the negative effects of short-term antibiotic treatment on the beneficial gut bacteria populations in infants," said lead author Catherine Staunton from Teagasc.
"By altering the gut microbiota and thus the immune system very early in life, the antibiotics could negatively influence long-term health, particularly by increasing the risk of developing asthma, allergy, and obesity.
"The risk is heightened by the fact that the antibiotic-driven disruption of the microbiota comes at a time when this population is in rapid flux and can easily be unbalanced."
Eight weeks after the infants were treated with antibiotics, the diversity of gastrointestinal flora remained diminished, although the number of individual bacteria was back to normal.
Of particular concern was the presence of a potentially disease-causing bacteria in treated infants.
It was unclear, however, whether the bacteria had outgrown the beneficial ones because their population had grown or because the others had shrunk.
However, Dr Stanton said the data suggested the potentially harmful bacteria had increased at the expense of the beneficial ones and that tied in with previous research.
The study, financed by Science Foundation Ireland and the Department of Agriculture, Food, and Marine, was published in the journal Antimicrobial Agents and Chemotherapy.
A similar four-year project, Infantmet, also funded by the Department of Agriculture, is looking at the gut development of 100 breast fed healthy infants and 50 babies born prematurely at Cork University Maternity Hospital.
Dr Stanton, who is involved in the study that began a year ago, said it was aimed at developing smarter infant formula that could promote the same bacteria as in breast-fed babies.
Early results from the study are expected later this year.