Our bodies are host to trillions of microbes - we have microbiomes, and they have a significant influence on our health. Most of those microbes are harmless, and many perform beneficial or even essential functions. New research has suggested that we may also be helping those microbes develop antimicrobial resistance because the human gut microbiome can act as a crucial reservoir of antimicrobial resistance. The study also noted that regardless of personal habits, the individual is influenced by the way antibiotics are consumed at the national level. The report has been published in Nature Communications.
While they can be important tools for preventing infection, antibiotics can also cause serious harm to the gut microbiome, and may increase the movement of resistance genes within the microbiome. They can deplete the number of good microbes, which can give nasty germs an opening to dominate the microbiome or infect cells. Genes can move easily from one microbe to another, a process well-documented as horizontal gene transfer, and research has also shown that antimicrobial resistance genes can migrate easily too, regardless of the health and lifestyle of the host.
Antimicrobial resistance is becoming a serious enough problem that the World Health Organization and other experts are warning about the threat it poses to human health. Antibiotic resistance caused the death of an estimated 1.27 million people worldwide in 2019. The widespread misuse and overprescription of antibiotics has been thought to contribute to this problem.
Even healthy people who have not used antibiotics recently are constantly bombarded with new microbes when they interact with people or pets, causing resistance genes to become embedded in their own microbiome. When people live in a country where antibiotic use is particularly high, more resistance genes can be found in their microbiome, explained co-corresponding study author Professor Chris Quince of the Earlham Institute and Quadram Institute.
In this study, the researchers assessed over 3,000 healthy human gut microbiomes that were sampled in 14 countries. All the microbial genes were sequenced with metagenomics, and the resistance genes that were identified, enabling the investigators to learn more about how these genes were moving. A median of 16 resistance genes were found in each sample that was analyzed. The median number of resistance genes varied among the 14 countries; between the lowest level in Netherlands, and the highest in Spain, there was a five-fold difference.
This work showed that there is a strong association between how frequently resistance genes were found in a specific country, and how many antibiotics the population of that country consumes. If antibiotics are taken with greater regularity, there are more resistance genes circulating among the population, said Quince.
Our bodies are helping the movement of resistance genes, because we constantly import and export microbes, some of which are pathogenic, Quince added. The microbial strains share genes, so if we're going to tackle antibiotic resistance, we have to do so at the micro and macro levels.
"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," added study co-author Professor Falk Hildebrand of the Quadram Institute.
Sources: Earlham Institute, Nature Communications