Here Come the Superbugs? – Antibiotic Resistance Heightened by Exposure to Pesticides and Herbicides

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A new study, published in the American Society for Microbiology’s journal mBio, finds that herbicides, particularly those used on genetically modified crops, can make antibiotics less effective.

The study found that individuals who are exposed to herbicides while taking antibiotics are more likely to need higher doses of antibiotics to fend off the offending bacteria.

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Jack Heinemann, the study’s lead author told The Guardian that policy makers and researchers need to begin looking at other factors in the fight against antibiotic resistance, notably the increased use of herbicides on genetically modified crops. “The countries that are growing GM crops at scale may wish to include these unanticipated effects on microbes in their evaluations,” Heinemann said.

The researchers used herbicide levels higher than what’s normally found residually on food, but at levels lower than standards for commercial crop growing, and is often similar to exposure levels for rural communities exposed to herbicide drift from nearby agricultural fields. The herbicides used included dicamba (sold commercially under the name Kamba); 2,4-dichlorophenoxyacetic acid; and glyphosate (Roundup), along with five different classes of antibiotics: ampicillin, ciprofloxacin, chloramphenicol, kanamycin, and tetracycline.

“The exposure pathways that we identified as possibly being the most relevant for future study generally arose from the use of the herbicide by others – for example, in the urban setting” Heinemann said. “Therefore, it may take communities talking to each other to find ways to reduce unintended exposures.”

While the research did note an increased antibiotic need when exposed to the herbicides, it wasn’t clear if it was the active ingredients in the herbicides or inactive ingredients. “If it turns out to be the inactive ingredients that reduce the potency of antibiotics, that could implicate a wider range of herbicides, as several available products have different active ingredients but the same inactive ingredients,” reports The Guardian.

The researchers are also looking into the most relevant impacts on human health as well as for farm animals, pets and pollinators, such as honeybees.

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