Antimicrobial resistance (AMR) genes spread easily through a population and it is heavily influenced by national trends in antibiotic consumption, regardless of a person's own health and habits, finds a study.

The study, published in the journal Nature Communications, suggested that the community of microbes living in and on human bodies may be acting as a reservoir for antibiotic resistance.

So far it was known that AMR genes can spread incredibly fast between gut bacteria, "quantifies the impact national antibiotic usage has on our commensal bacteria".

But the study, for the first time, showed 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 from the Earlham Institute and Quadram Institute in the UK.

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," explained Professor.

"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."

"If they exist in a population with a heavy burden of antibiotic consumption, it leads to more resistance genes in their microbiome," Quince said.

Their findings were based on an analysis of over 3,000 gut microbiome samples collected from healthy individuals, who were not taking antibiotics, across 14 countries.

The team carefully catalogued and recorded the number of antimicrobial resistance genes found in the samples by comparing data to the Comprehensive Antibiotic Resistance Database, a public health resource where resistance genes are documented.

They identified a median of 16 AMR genes per stool sample analysed. They also found that the median number of genes varied across the 14 countries for which they had data.