A new study has found links between antibiotic use in infants, changes in gut bacteria, and the development of disease when the child becomes an adult.
Imbalances in human gut microbes – the growth of harmful organisms or overgrowth of normally harmless microorganisms in the digestive tract - have been tied to infectious diseases, allergies and other autoimmune disorders, and even obesity, in later life.
Antibiotics - as opposed to anti-vaccines which are different - are by far the most common prescription drugs given to children, and widely considered one of the most over-prescribed drugs. Other studies have shown that antibiotics may have profound short and long-term effects on the diversity and composition of the bacteria in our bodies, called our microbiome.
The study, conducted by researchers at the University of Minnesota in the United States and published yesterday in the scientific journal Cell Host & Microbe, reviewed hundreds of research papers from around the world and found evidence of strong relationships between antibiotic use, changes in gut bacteria, and disease in adulthood.
"Diseases related to metabolism and the immune system are increasing dramatically, and in many cases we don't know why," says the study's senior author, Dan Knights, a biologist and assistant professor in the University of Minnesota.
"Previous studies showed links between antibiotic use and unbalanced gut bacteria, and others showed links between unbalanced gut bacteria and adult disease.” Knights and his team theorised that there may be a further link.
Gastrointestinal development begins in the womb, the study says. While the tract is considered sterile at birth, within hours microbial organisms from the mother’s skin, milk and environment begin to colonise the gastrointestinal tract.
Exposure to these microbes – a huge variety of dietary antigens (a huge variety of substances that activate the immune system to produce antibodies), hormones, growth factors and bacteria – is essential for proper function throughout life, the study says.
However, it takes two years before an infant gut completes a series of dynamic changes in chemistry and composition before the gastrointestinal tract becomes the same as an adult gut. This period is also crucial in the development of the immune system and its future efficiency but antibiotics can markedly affect the way these parallel developments work.
In the case of allergies, for example, the use of antibiotics may eradicate key gut bacteria that help immune cells mature. These cells would have been essential for keeping the immune system at bay when confronted with an allergen (a type of antigen that produces an abnormally strong immune response to fight off a perceived threat that would otherwise be harmless).
Even if these bacteria return, the study found, the immune system remained impaired.
"We think these findings will help develop a roadmap for future research to determine the health consequences of antibiotic use and for recommendations for prescribing them," Knights says.