Antimicrobial resistance (AMR) is an escalating global crisis, responsible each year for over a million deaths worldwide. The alarming rise in multidrug-resistant bacteria has predominantly been attributed to the misuse and overuse of antibiotics. However, groundbreaking new research reveals a surprising non-antibiotic culprit that may be significantly contributing to this menace: the widely used agricultural herbicide glyphosate. Scientists have discovered that certain multidrug-resistant bacteria, particularly those isolated from hospital settings, also exhibit formidable resistance to glyphosate, suggesting that weedkillers may unintentionally select for antibiotic resistance in environmental bacterial communities.
The study was spearheaded by Dr. Daniela Centrón at the Institute of Medical Microbiology and Parasitology in Buenos Aires. Her team conducted exhaustive experiments on bacterial strains collected from diverse environments, ranging from hospital infections to agricultural soils and protected wetlands. The core finding was that common species of multidrug-resistant hospital bacteria not only resisted multiple antibiotic classes but were also impervious to high concentrations of glyphosate-based herbicides. This finding is remarkably counterintuitive, as glyphosate is designed to target plants rather than bacteria, indicating a complex co-selection mechanism at play.
Between 2018 and 2020, researchers meticulously gathered 68 bacterial isolates from sediments within the Paraná delta, a critical wetland ecosystem located north of Buenos Aires. This region experiences glyphosate application in adjacent farmlands, yet within the reserve itself, herbicides have never been used. The isolates represented a broad taxonomic diversity, including genera such as Acinetobacter, Pseudomonas, Exiguobacterium, and Chryseobacterium. The team evaluated these strains for their susceptibility to an array of 16 common antibiotics alongside pure glyphosate and glyphosate-based herbicide formulations.
The isolates from the Paraná delta demonstrated varied levels of glyphosate tolerance despite their natural habitat being free of glyphosate contamination. Particularly notable were Enterobacter strains that withstood glyphosate concentrations up to 80 milligrams per milliliter, surpassing what might be expected in such environments. Conversely, soil-dwelling Bacillus strains displayed heightened sensitivity, with growth inhibited at concentrations as low as 2.5 milligrams per milliliter. The environmental strains’ partial resistance implies that glyphosate tolerance is phylogenetically widespread and possibly ancient, but its increasing agricultural usage could promote more resistant populations.
To provide a comparative clinical perspective, the study included 19 strains obtained from local hospitals, confirming pervasive antimicrobial resistance. Strikingly, 74% of these hospital strains were resistant to carbapenems—broad-spectrum antibiotics regarded as the last line of defense against difficult infections. Yet beyond antibiotic resistance, a universal trait among these clinical isolates was high resistance to glyphosate and glyphosate-based herbicides. This remarkable dual resistance challenges the traditional view that resistance evolves solely under direct antibiotic pressure and introduces environmental herbicides as a parallel selective force.
The implications of these results extend significantly beyond basic science. If multidrug-resistant pathogens originating in clinical settings enter the environment via untreated wastewater, they could exploit herbicide application zones as reservoirs where glyphosate acts as a selective agent. This interaction would facilitate the persistence and amplification of clinically dangerous bacteria in agricultural soils, bridging human health concerns with environmental practices. First author Dr. Camila Knecht emphasized the urgent need to recognize these pathways to mitigate the indirect spread of resistant strains.
Further analysis of the genetic relationships among the 102 bacterial strains through phylogenetic mapping revealed that glyphosate resistance clusters closely track bacterial lineages rather than geographical source. Resistant genera were consistently found across hospitals, feedlots, agricultural soils, and even the pristine Paraná delta, indicating that glyphosate resistance traits are broadly disseminated and horizontally transferable. This genetic proximity supports a dynamic gene flow between environmental reservoirs and clinical settings, exacerbated by overlapping human activities and waterborne transmission routes.
These findings underscore the multifaceted complexity of AMR ecology, where human agricultural interventions intertwine with microbial evolution in unexpected ways. The dual pressures exerted by antibiotics and herbicides in distinct but connected niches create a web of selective forces promoting bacterial adaptability. As Dr. Jochen A Müller from Karlsruhe Institute of Technology notes, the water cycle acts as a critical conduit facilitating bidirectional spread and recombination of resistance genes between environmental and clinical ecosystems.
Glyphosate, a cornerstone of modern farming for weed control, has long been fraught with controversy due to its detrimental effects on non-target species like pollinators and its classification as a probable human carcinogen by the International Agency for Research on Cancer. In some European countries, including France, Belgium, the Netherlands, and Germany, regulatory frameworks have introduced bans or restrictions to limit its use in sensitive areas. This study adds yet another layer of caution, flagging glyphosate’s unintended role in antibiotic resistance dissemination, an issue with profound public health ramifications.
Recognizing the urgency, Dr. Centrón advocates for a paradigm shift in pesticide regulation. She recommends mandatory co-selection testing for antibiotic resistance in any pesticide approval process and explicit warning labels on glyphosate products highlighting the risks of antibiotic resistance gene spread. This call for integrated policy reflects the growing understanding that antimicrobial resistance is a complex Umwelt phenomenon requiring cross-sectoral interventions spanning public health, agriculture, and environmental protection.
In conclusion, this pioneering research delivers a stark warning from the microbial frontline: the spread of multidrug-resistant bacteria is not solely a function of antibiotic usage but is also influenced by agricultural biocides like glyphosate. The convergence of resistance traits across clinical and environmental bacteria signals the necessity for holistic strategies to monitor, manage, and curtail all drivers of antimicrobial resistance. As glyphosate continues to be ubiquitous in global agriculture, understanding and mitigating its collateral microbial impacts will be essential to safeguarding the effectiveness of antibiotics, preserving ecosystems, and protecting public health on a planetary scale.
Subject of Research: Not applicable
Article Title: Glyphosate resistance as a potential driver for the dissemination of multidrug-resistant clinical strains
News Publication Date: 24-Mar-2026
Web References:
References:
- Article published in Frontiers in Microbiology, DOI: 10.3389/fmicb.2026.1740431
Image Credits: Not provided
Keywords: Antimicrobial resistance, glyphosate, multidrug-resistant bacteria, herbicide resistance, hospital bacteria, agricultural soils, co-selection, Paraná delta, carbapenem resistance, environmental microbiology, antibiotic resistance dissemination, bacterial phylogeny
