A common agricultural herbicide may be quietly engineering bacteria that can shrug off multiple antibiotics at once, according to new research that expands the blame for the global antimicrobial resistance crisis beyond hospitals and clinics.
Scientists discovered that glyphosate, sprayed across millions of acres worldwide, appears to select for bacteria resistant not only to the herbicide itself but also to a broad range of antibiotics used to treat human infections. The finding suggests that drug resistance is being shaped by chemical pressures in farming regions and soil, not just in hospitals where antibiotics are overused.
Researchers led by Dr. Daniela Centrón at the Institute of Medical Microbiology and Parasitology in Buenos Aires analyzed 102 bacterial strains collected from three distinct environments: a protected wetland in Argentina that had never been exposed to herbicides, nearby agricultural lands heavy with glyphosate use, and local hospital samples known for harboring multidrug-resistant pathogens.
Every single bacterium pulled from the pristine Paraná delta wetland showed at least some resistance to glyphosate, despite the fact that the chemical had never been applied there. The researchers concluded that glyphosate use in surrounding farmland was somehow selecting for resistant bacteria that then migrated into the protected area through water and soil.
The hospital strains told an even darker story. All of the multidrug-resistant bacteria obtained from hospitals were highly resistant to glyphosate and glyphosate-based herbicides. Worse, 74% of the hospital samples resisted carbapenems, a class of broad-spectrum antibiotics kept in reserve for severe infections when other options fail.
"If these bacteria enter the environment through untreated wastewater from hospitals, they could go on to thrive in agricultural areas where glyphosate is used," said Dr. Camila Knecht, the study's first author, pointing to a troubling two-way exchange between healthcare facilities and farming regions.
The genetic analysis revealed something striking: bacteria with the highest glyphosate resistance were often closely related across all three environments. This suggests that the same microbial lineages are evolving resistance to the herbicide in soil while simultaneously acquiring antibiotic resistance genes in hospitals, then shuttling those adaptations back and forth through water systems and human contact.
Glyphosate, first registered in the United States in 1974, is best known through Roundup. Modern consumer Roundup products sold at hardware stores have been reformulated and no longer contain glyphosate. But professional and agricultural versions, used on farms and in commercial landscaping, still rely heavily on it.
The stakes are measured in lives. Antimicrobial resistance kills an estimated 1.1 million to 1.4 million people globally each year. Until now, the crisis has been primarily attributed to misuse of antibiotics in medicine and livestock farming. This research suggests that herbicide regulation has been overlooking a parallel driver of resistance evolution in the soil microbiome.
The researchers are calling for a fundamental shift in how pesticides are evaluated before they reach the market. They argue that new herbicides and other chemicals should undergo testing to see whether they co-select for antibiotic resistance in bacterial communities. They also propose that pesticide labels should warn about the risk of spreading antibiotic resistance genes through contaminated water into treated drinking supplies and hospitals.
Glyphosate has faced scrutiny for other reasons as well. The International Agency for Research on Cancer classifies it as a probable human carcinogen, and research has shown it can harm arthropods including bees. Several European nations have already moved to restrict it. France, Belgium, and the Netherlands banned it for household use, while Germany prohibits application in public spaces.
The study was published in Frontiers in Microbiology in 2026, providing a fresh angle on how industrial chemicals in agriculture may be reshaping the microbial world in ways that ultimately circle back to threaten human health.
Author Jessica Williams: "This research pulls back the curtain on a blind spot in pesticide regulation, revealing that the war on weeds may be quietly training bacteria to survive our strongest medicines."
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