The widespread use of antibiotics has driven a meteoric rise in antimicrobial resistance whichis recognised currently as one of the most serious threats to global health.
Now, new research has found that, despite your own antibiotic use, the number of antimicrobial resistance (AMR) genes in your gut microbiome is heavily influenced by national trends in antibiotic consumption.
The study in the journal Nature Communications, suggests that AMR genes spread so easily through microbial populations, that our bodies may be acting as a reservoir for antibiotic resistance.
“Even a healthy individual, who hasn’t taken antibiotics recently, is constantly bombarded by microbes from people or even pets they interact with, which leads to resistance genes becoming embedded in their own microbiota,” explains co-senior author Chris Quince, Professor at the Warwick Medical School at the University of Warwick.
“If they exist in a population with a heavy burden of antibiotic consumption, it leads to more resistance genes in their microbiome.”
While the use of antibiotics can prevent the growth of, or kill, disease-causing bacteria, it can also lead to collateral damage to the rest of the microbiome – the collection of microbes that naturally live in and on our bodies, the majority of which aren’t pathogenic – and the development of AMR genes.
Researchers analysed more than 3,000 gut microbiome samples collected from healthy individuals across 14 different countries, comparing the AMR genes identified in the samples to those in the Comprehensive Antibiotic Resistance Database.
“We deliberately focussed on samples from healthy people, or at least those we could be confident weren’t taking antibiotics. We needed to see the gene profile in the gut microbiome without the influence of any antimicrobials,” explains Quince.
They identified a median of 16 AMR genes per stool sample, and that number varied across the 14 countries – with a five-fold variation between the lowest levels (in the Netherlands) and the highest (in Spain).
“We found that, in countries where antibiotics are taken more regularly, their populations also have higher numbers of resistance genes in their gut microbiome,” says Quince.
This is all due to the fact that our microbiomes aren’t isolated systems, with microbes constantly being transmitted between humans, and because of horizontal gene transfer – where microbes in our bodies can share genetic information, such as AMR genes, between each other.
“Our bodies are continually importing and exporting microbes and pathogen strains,” says 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.”
Co-author Falk Hildebrand, also a Professor at the Quadram Institute, says: “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 to investigate this relationship in more countries to inform public health strategies.