Popular Weedkiller Tied to Antibiotic Resistance

From Rodale News

Scientists just discovered a nasty little secret regarding America’s go-to weedkiller, Roundup: It changes disease-causing bacteria in a way that makes antibiotics humans rely on less likely to work.

While there have been many studies looking at Roundup’s acute toxicity—how much it would take to poison someone or something—to the study authors’ knowledge, this is the first time scientists have looked at the effects that lower, sublethal exposures of herbicides have on bacteria, particularly species that can cause diseases in people and domestic animals.

Antibiotic resistance is a big and growing problem. I think that a key lesson of this work is that we have to think more broadly, holistically, about medicine and the environment and not think that because herbicides are used on plants and antibiotics are used on people that they don’t have any relevance when they mix together somewhere,” says study author Jack Heinemann, PhD, professor and lecturer of genetics at the University of Canterbury in New Zealand. “We and our animals, and some of our most important pollinators, move through environments that have both of these kinds of chemicals and many more, many of which have only been introduced at commercial scales in the last several decades. We should, in my opinion, consider whether long-term, small doses of some chemicals may work against attempts to restore the efficacy of antibiotics.”

The study appears online in the peer-reviewed journal of the American Society for Microbiology, mBio.

In the lab study, researchers found that commonly used agricultural and home-use weedkillers Roundup (glyphosate), Kamba (dicamba), and 2,4-D change the bacteria’s response to commonly used antibiotics, including tetracycline and ciprofloxacin. This change occurs at levels commonly used on farm field crops, lawns, gardens, and parks. The authors say this could lead to the growing issue of antibiotic resistance, particularly threatening farmworkers, farm animals, and bees in rural settings, along with children and pets taking antibiotics in urban settings where herbicides are used.

“In our study we used Roundup, the actual commercial product, and not purified active ingredient glyphosate. We also used commercial formulations based on dicamba and 2,4-D. We studied the product that is actually used as a herbicide,” says Heinemann.

The way Roundup causes this effect is likely by causing the bacteria to turn on a set of genes that are normally off, Heinemann says. “These genes are for ‘pumps’ or ‘porins,’ proteins that pump out toxic compounds or reduce the rate at which they get inside of the bacteria,” he explains. “Once these genes are turned on by the herbicide, then the bacteria can also resist antibiotics. If bacteria were to encounter only the antibiotic, they would instead have been killed. In a sense, the herbicide is ‘immunizing’ the bacteria to the antibiotic.”

The authors say the unexpected findings bring up an important point. “Many kinds of commercial products that we use around the home, in the environment, or in our workplaces can have effects on us or other organisms that we don’t think about,” they say.

“Because we are familiar with the product, we shouldn’t lose our respect for its potential to cause effects we ourselves just haven’t thought about, and not all of these are an acute toxic reaction that is relatively obvious,” they caution.

The best way to avoid these harmful weedkillers is to choose organic whenever possible, use these organic lawn-care tricks, and elect lawmakers who support real chemical regulation reforms, not weak ones supported by the chemical industry.



By LEAH ZERBE for rodalenews.com