Antibiotic resistance is not a new topic. In 2013, reports from both the CDC and World Health Organization issued stern warnings about this growing problem with the CDC estimating “more than two million people are sickened every year with antibiotic-resistant infections, with at least 23,000 dying as a result” (see CDC report here).
Now it appears another factor has implications in this concerning issue. New research indicates at least three different commonly used herbicides effect the susceptibility of bacteria to antibiotics, meaning these herbicides are changing the way bacteria respond to antibiotics. A new study published in the American Society for Microbiology journal mBio looked at both E. coli and Salmonella bacteria exposed to three different herbicides; Dicamba (Kamba), 2,4-Dichlorophenoxyacetic acid (2,4-D) and Glyphosate (Roundup).
The study showed that when these bacteria were exposed to the herbicides occasionally it had no effect or it made the bacteria more susceptible to antibiotics. However in the majority of cases, exposure to these weed sprays actually increased their resistance to multiple types of antibiotics. Not only that, but when the bacteria responded to the presence of the herbicides, some resistance values increased 6-fold. The antibiotics used in this study included ampicillin, ciprofloxacin and tetracycline’s, all of which are widely used to treat disease.
The levels of herbicides tested were within the standard application levels for each product, all of which were purchased at a local store. Herbicide chemicals are commonly used in food production, parks, and many household gardens.
Implications in the global epidemic
The study authors stated that “The magnitude of the induced response may undermine antibiotic therapy and substantially increase the probability of spontaneous mutation to higher levels of resistance.” And thus, addressing this global epidemic requires a broader approach by looking into a multitude of contributors to the evolution of resistance. It appears that herbicide use can now be added to the list of concerning issues which include the overuse and misuse of antibiotics in medicine and livestock production.
The study authors suggested there is a small chance that exposure to the herbicides through food would produce these effects, but it could be a concern to people in areas where pesticides are being used like farmers, workers and others who live near agricultural areas.
This is yet another instance where eating organically produced food can help. Not only are the fruits and vegetables produced without the use of herbicides, but eating organic produce puts pressure on conventional farming practices. The more people eat organic, the more the industry will trend towards organic farming practices.
References and Resources
1. Centers for Disease Control and Prevention. Antibiotic resistance threats in the United States, 2013. http://www.cdc.gov/drugresistance/threat-report-2013
2. Sublethal Exposure to Commercial Formulations of the Herbicides Dicamba, 2,4-Dichlorophenoxyacetic Acid, and Glyphosate Cause Changes in Antibiotic Susceptibility in Escherichia coli and Salmonella enterica serovar Typhimurium. Brigitta Kurenbacha, Delphine Marjoshia, Carlos F. Amábile-Cuevasb, Gayle C. Fergusonc, William Godsoed, Paddy Gibsona, Jack A. Heinemanna. http://mbio.asm.org/content/6/2/e00009-15.full#ref-2