Herbicides Found To Increase Antibiotic Resistance In Disease-Causing Bacteria

Via: Balefire | Shutterstock


by Luke Sumpter

on October 1, 2015

A research team from the University of Canterbury in New Zealand has determined that various widely used herbicides can cause bacteria to build up a resistance to antibiotics. These include the world’s most commonly used herbicide Roundup, produced by agrochemical and biotechnology giant Monsanto.

Roundup contains a chemical named glyphosate, which has been described by Dr. Stephanie Seneff, Senior Research Scientist at the MIT Computer Science and Artificial Intelligence Laboratory, as “the most important factor in the development of multiple chronic diseases and conditions that have become prevalent in the Westernized societies.”

Other herbicides tested included Nufarm’s Kamba as well as 2,4-D. The latter is a chemical that is a key ingredient in a herbicide developed by Dow AgroSciences. In June 2012, Reuters published a report detailing the findings of a World Health Organization unit that stated 2,4-D “possibly” causes cancer in humans.

Upon reading such reports, it becomes quite baffling as to why these chemicals are sprayed upon the very food that we depend on consuming to fuel the healthy growth and maintenance of our bodily systems. And it doesn’t quite fall in alignment with reason and common sense that our society would allow these chemicals into the delicate and developing bodies of the next generation.

The research team from the University of Canterbury has now found evidence that raises further concerns over the safety of these chemicals via their investigations into what occurs when certain disease-causing bacteria are exposed to the aforementioned herbicides.

Reset spoke to Professor Jack Heinemann of the University of Canterbury’s School of Biological Sciences who led the research.

When asked about the motivating factor behind the pioneering study, he says, “The first source of inspiration was that I noticed the active ingredient dicamba of the herbicide sold locally as Kamba had structural similarity to salicylates. These have been shown in the 1980s to cause resistance. 2,4-D was included in the study for the same reason. Initially, due to its different chemistry, Roundup (with active ingredient glyphosate) was chosen for contrast.”

Heinemann adds that his “second source of inspiration was the realization that these three herbicides are among the most commonly used worldwide and use has either increased dramatically, in the case of Roundup, or is expected to in regards to 2,4-D and Kamba. They are used in agriculture, but also in urban settings and around homes.”

Photo: Tractor spraying pesticides on soy bean crop. Via: Fotokostic | Shutterstock.

Photo: Tractor spraying pesticides on soy bean crop. Via: Fotokostic | Shutterstock.

Upon administering the herbicides to the bacterial strains, the team came across results that are indeed quite alarming. Heinemann tells Reset, “We found that exposure to commercial formulations of very common herbicides can cause bacteria to change their response to antibiotics. They often become more resistant, but we also saw increased susceptibility or no effect. The direction or magnitude of the observed effects were not predictable from the bacterial species, antibiotic or herbicide used.”

So did the research team determine that any of the herbicides tested were more dangerous than others with regards to catalyzing antibiotic resistance? Heinemann replies, “Most of the effects were of a higher magnitude when we used Kamba or Roundup than 2,4-D. But ‘danger’ is not a simple extrapolation of this effect. Any danger depends on the effect, but also the exposure pathway and the likelihood of the exposure which might vary from place to place and herbicide to herbicide.”

If herbicide exposure can indeed prompt disease-causing bacteria to build up a resistance to antibiotics, what concentrations are required to trigger this effect? Heinemann says, “The effects were detectable at herbicide concentrations that were above currently allowed residue levels on food. However, they were within the range of concentrations encountered during application of the herbicides.”

Does this mean, that if bacterial resistance is generated even when herbicide is applied in accordance with legal restrictions in terms of concentration, that safety regulations need to be revised? Heinemann says, “This is a complicated question for several reasons. Importantly, the effects occur at concentrations above legally allowed levels in food. However, the effects of different kinds of agents are additive. For example, we found that aspirin and Kamba could induce the effect when together at concentrations that neither could on its own. The concentrations that may be in some (farm) animal feed in theory could be high enough to induce the effect. For example, it is legal in New Zealand (and probably other countries too) to graze farm animals on paddocks recently sprayed with Roundup concentrations that can cause this effect.”

Heinemann continues, “Finally, it matters how your food got exposed. You personally might not use the herbicide, but if you stroke your cat that just walked through a neighbor’s sprayed lawn and then pick up your sandwich, well, who knows?”

Via: Jay Ondreicka | Shutterstock

Via: Jay Ondreicka | Shutterstock

Even though these negative effects were not observed in concentrations of herbicide that are allowed to be present in the food supply, what implications may arise if we are consuming small amounts over a long period of time? Heinemann states, “We are only now testing whether peak concentration or long exposure to lower concentrations might be more important. I think that we are getting some interesting results but I’ll have to leave it there till they’ve been through peer review.”

Considering the detrimental problems that the herbicides in question can potentially inflict, both in terms of antibiotic resistance and in light of cancer concerns, it is time to start questioning the true value of such farming practices? Is it really worth exposing ourselves to these chemicals — at any level — just to prevent the growth of weeds, which can be regulated in more natural ways?

When asked about his stance on organic produce versus that which is conventionally grown Heinemann says, “We haven’t tested products approved for use in organic agriculture. The only comment I would make is that a production method that emphasizes not using pesticides is by default more attractive to me because I expect that no matter what pesticides might be used or might be approved for use, their use is intended to be less. From the few studies I’ve seen, I don’t think that expectation is likely to be wrong.”