What is already known on this topic
The human gut microbiota has emerged as a reservoir for bacteria harboring genes that help them to fight off antibiotics. But how antimicrobial resistance arises in early life remains unclear.
What this research adds
By analyzing stool samples from more than 650 one-year-olds in Denmark, researchers found that the infants’ guts are home to bacteria, such as Escherichia coli, that harbor hundreds of antibiotic-resistance genes. The use of antibiotics during pregnancy and the presence of older siblings in the household appear to influence the number of antibiotic-resistance genes in the gut microbiota. What’s more, higher levels of antibiotic-resistance genes are associated with a specific gut microbial composition that is linked to a heightened risk of developing asthma later in life.
The findings could be used to inform public-health interventions aimed at reducing the spread of antimicrobial resistance, especially among pathogenic bacteria.
The emergence of antimicrobial resistance is one of the most pressing public-health threats. Now, researchers have found that the infant gut is home to bacteria that harbor hundreds of antibiotic-resistance genes. The distribution of such genes is influenced by several factors, including the use of antibiotics during late pregnancy.
The findings, published in Cell Host & Microbe, could help to inform public-health interventions to mitigate the spread of antimicrobial resistance, the researchers say.
In the past years, the human gut microbiota has emerged as a reservoir for bacteria harboring genes that help them to fight off antibiotics. But how antimicrobial resistance arises in early life remains unclear.
To investigate this, Søren Johannes Sørensen at the University of Copenhagen and his colleagues collected stool samples from 662 one-year-olds in Denmark and analyzed the microbial DNA present in the samples.
The researchers found 409 types of antibiotic-resistance genes that conferred resistance to 34 classes of antibiotics. Of these antibiotic-resistance genes, 167 conferred resistance to more than one antibiotics.
All children had at least one type of gene that conferred resistance to multiple antibiotics, including antimicrobial drugs classified as critically important by the World Health Organization. These genes were present even though the children had not taken those drugs.
The team found that the stool samples could be grouped into two main clusters based on the abundance of antibiotic-resistance genes, with Escherichia coli being the most abundant species in one of the clusters. About 55% of all antibiotic-resistance genes in this cluster were from E. coli, the researchers found.
In general, Proteobacteria such as Escherichia, Klebsiella, and Enterobacter harbored the largest number of antibiotic-resistance genes in the infant gut. Proteobacteria are known for being responsible of several infections and for being able to transfer their DNA to other bacteria.
To assess how different environmental factors can influence the distribution of resistance genes, the researchers looked at frequency of antibiotic use, presence of siblings, type of home, and mode of delivery — among other things.
The abundance of resistance genes was influenced by several factors, for example whether the children grew up in rural or urban environments. Children living in an urban area had higher levels of resistance genes than children living in a rural area. The presence of older siblings in the household and the use of antibiotics during late pregnancy also influenced the distribution of genes in the infant gut.
Further analyses showed that higher levels of antibiotic-resistance genes tend to be associated with a specific gut microbial composition that is linked to a heightened risk of developing asthma later in life.
Although the role of antibiotic-resistance genes in the development of the gut microbiota is still unclear, high levels of such genes could bring more health risks, the researchers say. The findings, they add, “can be used to support public health interventions aimed at decreasing transmission among pathogens.”