New Study: Glyphosate May Be Fueling the Rise of Deadly, Antibiotic-Resistant Superbugs

A new study published by Argentinian researchers found that glyphosate may be contributing to the growing problem of antimicrobial resistance (AMR), as drug-resistant bacterial strains are also tolerant to high doses of glyphosate. AMR is responsible for 1.1 million to 1.4 million deaths worldwide each year. The study was published in March in Frontiers in Microbiology.

Researchers collected 68 bacterial strains from a protected wetland where glyphosate has never been applied directly, but is common in nearby agricultural areas. They found that many of these bacteria, including Enterobacter species, survived high concentrations of glyphosate, exceeding typical agricultural application rates. 19 multidrug-resistant (MDR) strains were taken from hospital patients. These clinical isolates were resistant to multiple antibiotics and glyphosate.

“Here we show that the most common species of multidrug-resistant bacteria from hospitals are not only resistant to multiple antibiotic classes, but also to high concentrations of the weedkiller glyphosate,” said Dr. Daniela Centrón, senior author of the study and researcher at the Institute of Medical Microbiology and Parasitology in Buenos Aires. “These results suggest that weedkillers – which, unlike antibiotics, are widely applied in agricultural environments – may have the unintended side-effect of selecting for AMR among bacterial communities within the soil.”

Genetic analysis revealed similarities between the survival wetland species and hospital pathogens. Both survived by using efflux pumps – molecular systems inside bacteria that actively pump out toxins. Glyphosate exposure appears to strengthen these pumps, which also help expel antibiotics.

“This means that 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 lead author Dr. Camila Knecht.

Argentina is one of the world’s largest consumers of glyphosate for use on genetically modified corn, soy, and cotton. Use of glyphosate over time selects for stronger, more resistant bacteria, and those traits are passed on to the next bacterial generation. This is a process known as selective pressure that occurs in soil and water exposed to glyphosate.

These resistant organisms are sent into shared waterways via agricultural runoff. Hospital sewage goes into the same environment as the glyphosate-resistant bacteria. The bacteria exchange resistance genes in this environment, which work to create “superbugs” that even the strongest “last resort” drugs are unable to tackle.

“In the environment, the use of glyphosate leads to the evolution of resistant bacteria in impacted soils, whereas the use of antibiotics favors their evolution in hospitals. Bacteria carrying antibiotic resistance genes can spread and breed between those two niches in both directions and in multiple ways, with the water cycle playing a key role in transmission,” said coauthor Dr. Jochen A Müller.

This research comes amid Bayer’s continued lobbying efforts to secure manufacturer immunity for harms caused by Roundup and its primary ingredient, glyphosate. The company has held private meetings with Trump administration officials who have prior industry ties, in an apparent attempt to gain favor in the current Supreme Court case.

Lawsuits against Bayer have focused on individual harm caused by direct exposure to Roundup and a subsequent cancer diagnosis, most commonly Non-Hodgkin Lymphoma. Not only would these cases be difficult or impossible to bring against Bayer if the Supreme Court rules in favor of the company, but any potential cases regarding antimicrobial resistance caused by the use of glyphosate would likely be thrown out of court.

While the Supreme Court heard oral arguments on April 27 for the Bayer case, it is unknown whether the court will rule in favor of Bayer. If Bayer wins the case, plaintiffs would no longer be able to bring state-level failure-to-warn claims against the company. The EPA determines the requirements for a product’s warning label, and federal preemption would override any obligation for the company to warn the public about potential harms related to the product.

One of the authors of the Argentinian study suggested that there should be additional testing requirements for herbicides and pesticides to prevent antibiotic resistance, as well as warnings on the labels of approved products.

“Policies for the use of any pesticide, as well as its metabolites, should stipulate the requirement for co-selection testing with antibiotics before marketing,” said Centrón. “Labels should include a warning that genes for antibiotic resistance can spread from glyphosate-contaminated soils to hospitals through untreated water.”

According to the CDC, there are more than 2.8 million AMR infections every year in the United States and 35,000 deaths that occur as a result. AMR infections that require second and third-line treatments can cause serious side effects like organ failure and can prolong recovery for months. The CDC says medical advancements such as joint replacements, organ transplants, cancer therapy, and the treatment of diabetes, asthma, and rheumatoid arthritis require the ability to fight infections with antibiotics. Many AMR infections have no treatment options.