The team identified a median of 16 AMR genes per stool sample analysed. They also found the median number of genes varied across the 14 countries for which they had data.
For example, they saw a five-fold variation in median resistance levels between the lowest in the Netherlands and the highest in Spain.
Using World Health Organization and ResistanceMap data, the team were able to show a strong correlation between the frequency of resistance genes present in a country and national antibiotic consumption levels.
“We found that, in countries where antibiotics are taken more regularly, their populations also have higher numbers of resistance genes in their gut microbiome,” said Professor Quince.
The reason this collateral damage is such a major problem is that microbes are constantly sharing genes with each other. Known as horizontal gene transfer, this process helps AMR genes to spread back and forth between species.
“Our bodies are continually importing and exporting microbes and pathogen strains,” explains Professor Quince. “These strains are themselves passing genes back and forth, which means the challenge of AMR has to be tackled at both the micro and macro level.
“Given our complex relationship with microbes, we need to do more research to understand how we maximise the benefits and minimise the risks when it comes to guiding treatment decisions and developing new medicines.”
Dr Falk Hildebrand, research author at the Quadram Institute and Earlham Institute, said: “We’ve known for some years that antimicrobial resistance genes can spread incredibly fast between gut bacteria.
“This study is so important because it can, for the first time, quantify the impact national antibiotic usage has on our commensal bacteria, as well as giving us insights into the common types of resistance we can expect to evolve.”
The researchers plan to carry out further research - and encourage others to - in order to investigate the relationship in more countries and inform public health strategies.
The research was funded by UKRI-Biotechnology and Biological Sciences Research Council, UKRI-Natural Environment Research Council, and the European Research Council.
Population-level impacts of antibiotic usage on the human gut microbiome, is published in Nature Communications.
Kihyun Lee, Sebastien Raguideau, Kimmo Sirén, Francesco Asnicar, Fabio Cumbo, Falk Hildebrand, Nicola Segata, Chang-Jun Cha & Christopher Quince
Samples studied came from Austria, Canada, China, Germany, Denmark, Spain, France, Israel, Italy, Kazakhstan, Madagascar, Netherlands, Sweden, USA. Countries with fewer than 10 samples meeting the inclusion criteria were excluded.