Common herbicides benefit antibiotic-resistant bacteria, new study shows

The use of herbicides can increase the incidence of antibiotic-resistant bacteria in soil, according to a new study from the University of York.

Herbicides are one of the most widely used chemicals in agriculture, and although these compounds are used to target weeds, they can cause damage to soil microbes, such as bacteria and fungi, potentially altering the ecological properties of microbial communities.

Scientists from China and the United Kingdom have studied the effect of three widely used herbicides, glyphosate, glufosinate and dicamba, on the bacterial communities of the soil.

Using soil microcosm, researchers discovered that herbicides increased the relative abundance of bacterial species carrying antibiotic resistance genes. This was because mutations that improved growth in the presence of herbicides also increased bacterial tolerance to antibiotics. Herbicide exposure has also led to a regular movement of drugs that resist antibiotics between bacteria.

Similar patterns have been found in agricultural fields in 11 Chinese provinces where the history of herbicide applications, and the levels of herbicide residues in soils, have been linked to increased levels of resistance to genes against antibiotics.

Dr Ville Friman from the Department of Biology said: “Our results suggest that the use of herbicides may indirectly cause the development of antibiotic resistance in microbiomas in agricultural soils, which are repeatedly exposed to herbicides during weed control.

Interestingly, antibiotic resistance genes are preferred at herbicide concentrations that were not lethal to bacteria. This shows that very low levels of herbicides can significantly alter the genetic makeup of soil bacterial populations. Such effects are currently missed by ecotoxicological risk assessments, which do not. of prolonged chemical application to microbial communities.

“Although antibiotic genes are not harmful again, it will reduce the effectiveness of antibiotics during clinical treatments. Keeping the frequency of resistance genes low will prolong the long-term effectiveness of antibiotics. Could be a globally important source of resistance genes.”

The study concluded that the effects of these herbicide concentrations on microbial communities need to be reviewed to understand the associated risks for the occurrence of antibiotic resistance genes.

The study “Herbicide selection promotes resistance to antibiotics in soil microbiome” is published in Molecular biology and evolution.