Transparency's picture
Why did Monsanto patent Glyphosate as an antibiotic? Also, the medical establishment has been preaching for years that we should not overuse antibiotics, so as to prevent the development of super bugs. So, doesnt the generous use of the antibiotic Glyphosate as the Ag industrys go to herbicide contradict this line of thought?

A:Expert Answer

Answer at a Glance:
  • Companies with patented chemical technologies will generally try to patent all reasonable potential uses of that chemical in order to obtain maximal return on their research investments.
  • When glyphosate is used as recommended, it is not used in concentrations that are high enough for it to function as an antimicrobial.
  • Glyphosate is not used in clinical medicine (and has no relatives used in medicine, either); therefore, the use of glyphosate in agriculture has nothing to do with resistance to antibiotics used in human medicine.

Companies with patented chemical technologies will generally try to patent all reasonable potential uses of that chemical in order to obtain maximal return on their research investments. Such uses cannot be speculative — we can’t patent glyphosate as jet fuel or nail polish remover, because it clearly does not do those things — but glyphosate does inhibit an enzymatic pathway in many bacteria and parasites, and a reasonable case can be made that glyphosate might be effective as an antimicrobial. (Technically, an antibiotic is naturally occurring, while antimicrobial covers a broader range of compounds, but most people use the terms interchangeably today.) 

 

A lot stands between a compound with antimicrobial activity in the test tube and a clinically effective antimicrobial agent. Alcohol kills microbes, but taking a beer for your earache is not going to work — you can’t get a high enough alcohol concentration in the body to kill the bacteria without killing the patient first. Sufficiently high concentrations of glyphosate can kill microbes in a test tube, but to be effective clinically, one needs to be able to: 

 

  1. Achieve reliably effective concentrations with a reasonable oral (or IV) dose in humans. This is difficult to achieve with glyphosate, especially orally. 

 

  1. Have a workable dosing frequency, meaning you can take (or give) the antibiotic every 8-12 hours or less without the concentration falling below effective levels in the body. We used to give a lot of antibiotics every six hours or less, but compliance is very poor. Glyphosate has a short persistence in humans (half of an absorbed dose is excreted in around two hours).

 

  1. Affect microbes via a mechanism that still works in the body. Glyphosate blocks the production of certain amino acids in bacteria, and the bacteria will die, or at least stop reproducing, if they cannot obtain these nutrients from the environment … but blood and tissues are not water — they are chock-full of the nutrients that microbes need to survive. 

 

  1. Avoid toxicity to the patient. Here, glyphosate is actually a winner — it has extremely low mammalian toxicity, does not undergo metabolism and is rapidly excreted in urine.

 

The bottom line is that, to date, nobody has demonstrated that glyphosate is an effective antimicrobial agent for treating human or animal infections.

 

The overuse of antibiotics in humans and the intensive use in hospital settings is a major problem, but use of antibiotics in agriculture can sometimes result in the selection of antibiotic-resistant organisms, and these organisms may then cause problems in the form of resistant human infections. This matters only if a chemical (or a close relative with cross-resistance) is use in both clinical medicine and agriculture. Because glyphosate is not used in clinical medicine (and has no relatives used in medicine, either), the use of glyphosate in agriculture has nothing to do with resistance to antibiotics used in human medicine. 

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Comments

Transparency's picture

Also, please note that my punctuation disappears after I submit my questions...some kind of technical glitch. Thanks.

Transparency's picture

Thank you very much for the response. However, I'm not convinced the case is closed on this..

A recently published study by the American Society of Microbiology’s journal mBio has linked glyphosate and two other widely-used herbicides–2,4-D and dicamba–to antibiotic resistance.

From Civileats.com: This study found that exposure to these herbicides in their commercial forms changed the way bacteria responded to a number of antibiotics, including ampicillin, ciprofloxacin, and tetracycline–drugs widely used to treat a range of deadly diseases.

Dicamba, 2,4-D, and glyphosate have been in use for decades, so why have their antibacterial-resistance effects not been documented before? As the study’s lead author, Jack Heinemann, professor of genetics at the University of Canterbury in New Zealand, explains, when pesticides are tested for adverse effects, “it’s the lethal toxicity that people focus on.” In other words, how much of the chemical will kill an organism.

“What makes our study different, is that it is looking at a sub-lethal effect,” says Heinemann. “The effect we see requires that the bacteria stay alive.”

Previous studies done by other researchers have found that substances chemically similar to dicamba and 2,4-D can cause antibiotic resistance, Heinemann explains. So he and his colleagues decided to investigate whether these herbicides would produce similar effects. They added glyphosate to the study because it is chemically unlike the other two. But, to their surprise, it also produced some antibiotic resistance.

Heinemann explains that because these herbicides are not “supertoxic” to the bacteria the study tested–E. coli and Salmonella–they are not killed outright at levels typically used to kill weeds. Instead, the bacteria stay alive while activating proteins known as efflux pumps in order to rid themselves of toxins. And this defense mechanism can make the bacteria develop resistance to the threat from which it is defending itself.

Scientists know that overuse of antibiotics in humans can decrease their effectiveness. In the same way, says Heinemann, “exposure to these pesticides make the pathogens stronger.”

Although this study only looked at two laboratory strains of human pathogens, the antibiotics examined represent what he calls “broad classes” of drugs we’ve come to depend on to fight infections and the herbicides are three of the most-used worldwide.

Heinemann also notes that the different pesticides produced a variety of responses. While all three produced an antibacterial-resistant response to some of the antibiotics, some of the combinations his team tested produced no response and some increased the antibiotic’s effect.

Although the study is likely to be seen as controversial by some, University of Massachusetts Dartmouth assistant professor of biology, Dr. Mark Silby says it “followed established protocols” and the existing scientific literature supports its findings.

“This is a very carefully-designed study,” says Dr. Michael Hansen, a senior staff scientist at Consumers Union. “It’s incredibly important work showing the complexity of an effect that hadn’t been thought about before.” The mechanisms by which the bacteria respond to toxics–in this case herbicides–are already well-known, Hansen explains. What’s new and important is looking at non-lethal levels of exposure in combination with the antibiotics.

The weed-killers used in the study were purchased at a local store and were used at levels specified in use directions, which means the scientists were testing chemicals actually in use worldwide rather than a special laboratory sample of the active compound.

How could any of this affect people?

“These herbicides are now used at such a scale that we can almost use the term ubiquitous,” says Heinemann. For one, glyphosate is used on about 94 percent of the soybeans and 89 percent of the corn grown in the U.S, while 2,4-D is the third-most widely used herbicide in the U.S., while dicamba ranks fifth in use worldwide.

The levels at which the researchers saw effects were higher than the residues allowed on food, but below what is often used in rural settings, says Heinemann. The results of Heinemann’s study suggest there is probably a small chance that exposure through food would produce these effects, but they could be a concern in areas where the pesticides are being applied, says Hansen. Thus, the people most likely to be affected are farmers, farmworkers, and other people who live in agricultural communities." - See more at: http://civileats.com/2015/03/24/study-links-widely-used-pesticides-to-an...

So for farmers and citizens living in agricultural communities who may be exposed to pesticides on a daily basis, this study raises some interesting questions about pesticides/glyphosate and the development of antibiotic-resistant organisms.

nsv501's picture

Actually, glyphosate use does induce antibiotic resistance.
http://news.nationalgeographic.com/2015/04/150422-glyphosate-roundup-her...
http://mbio.asm.org/content/6/2/e00009-15
We need to err on the side of caution. We tend to just start using chemicals and drugs before we REALLY understand them. That is harming a lot of people.