Weed killers could make antibiotic drugs less effective, a new study warns. While herbicides are often used in agricultureWeed controlWhen used, scientists say they can cause damage to soil microbes such as bacteria and fungi, potentially altering the ecological properties of microbial communities.
The researchers found that mutations that improved bacteria's ability to survive and grow despite herbicides also made them more tolerant to antibiotics. Herbicide exposure also caused the bacteria to pass antibiotic resistance genes among themselves more frequently.
The study, led by researchers at the University of York, examined fields in Britain and 11 Chinese provinces. Researchers fear that fields treated with herbicides could be contributing to worrying levels of antibiotic-resistant infections in humans. Even very small amounts of common weed killers such asGlyphosate, glufosinate and dicamba led to increased antibiotic resistance.
Biologists say risk assessments often don't take into account the effects of herbicides on soil bacteria over long periods of time.
“Our results suggest that herbicide use could indirectly drive the development of antibiotic resistance in agricultural soil microbiomes that are repeatedly exposed to herbicides during weed control,” says Dr. Ville Friman from the university's biology department said in a statement. “Interestingly, antibiotic resistance genes were favored at herbicide concentrations that are not lethal to bacteria. This shows that even very small amounts of herbicides can significantly alter the genetic composition of soil bacterial populations.”
“Such effects are currently overlooked by ecotoxicological risk assessments that do not take into account the evolutionary consequences of prolonged chemical use at the level of microbial communities,” he continues. “Although antibiotic resistance genes are not harmful per se, they reduce the effectiveness of antibiotics in clinical treatments. If the frequency of resistance genes is kept low, the long-term effectiveness of antibiotics is extended. Because resistance genes can easily move between environments, agricultural fields worldwide could be an important source of resistance genes.”
The results were published in the journalMolecular Biology & Evolutionpublished.
