Background
Antibiotic resistance — bacteria evolving the ability to survive drugs designed to kill them — is one of the most urgent global health threats.
While the link between antibiotic use and resistance in hospitals is well established, what happens outside of hospitals has been much harder to assess.
Objective
This study tackled that question at an unprecedented scale, looking at antibiotic resistance genes in over 300,000 bacterial genomes collected from non-clinical, non-human environments — soils, lakes, rivers, farms, wildlife, and hot springs — across 44 countries.
It then checked whether the amount of antibiotics each country consumes nationally predicts how prevalent antibiotic resistance genes are in these bacterial genomes.
A total of 155 distinct resistance genes were tracked, covering 11 major drug classes.
Findings and implications
The findings were striking on two fronts. First, resistance is already remarkably widespread: any randomly chosen cell is expected to carry on average ~10 resistance genes, and a substantial portion of examined genomes contained over 10 such genes — meaning multi-drug resistance is common even outside hospitals.
In some countries the numbers were particularly high: for example, the probability that a given quinolone resistance gene is present in a given strain in Thailand was estimated at 42%, 35% in Pakistan, 33% in Poland, and 32% in Vietnam.
Second, and perhaps most importantly, strong positive correlations were found between nationwide antibiotic consumption rates and mean resistance gene prevalences for nearly all drug types — including sulfonamides and aminoglycosides, which showed the strongest associations.
This held not just for bacteria in general, but also specifically for known human pathogens.
The detection of these correlations is especially remarkable because many other country-level differences (regulations, climate, agricultural practices) are expect to weaken such correlations.
The results underline the urgency to develop national policies that curb the overuse of antibiotics, and show that reductions at the national level would benefit not just global public health (i.e., as a "public good") but would actually decrease resistance in the specific countries enacting those reductions.
Full article:
Louca, S. (2025). National antibiotic consumption is strongly related to the prevalence of antibiotic resistance across bacterial clades. iScience 28:111712 |
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