02
Jan
Mechanism for Escalating Antibiotic Resistance in Agriculture Detailed in Study, as Crisis Grows
(Beyond Pesticides, January 2, 2025) Adding to the body of scientific literature on the fast escalating antibiotic resistance crisis is a study published by Chinese scientists in Environmental Science & Technology, which shows that antibiotic resistance genes (ARGs) in soils move up through trophic levels via predation. Gut microbiomes of soil fauna have been found to be reservoirs of ARGs. How this process operates in soils is vital, because what happens in soil microbes does not stay there. If bacteria altered in soils move up trophic levels, ARGs may strengthen the multicellular agricultural pests the industry is trying to kill—insects, fungi, plants—not to mention bringing their libraries of resistant genes into the microbiomes of vertebrates, including humans.
Antibiotic resistance is a natural phenomenon, but human activity has greatly increased its presence in ecosystems the world over, including in one of the ecological niches of greatest concern to the future of food and human health: soils. Soils are complexes of mineral and organic substrates populated by billions of microorganisms and tiny animals. They are rapidly being degraded by conventional agriculture, forestry, and land management practices generally—more than a third of the world’s agricultural land has already been severely damaged by pesticides, fertilizers, water depletion, and loss of biodiversity.
As Beyond Pesticides reported last May, pesticides alter the microbial species composition in agricultural soils. A Russian study found microbial taxa known for high antibiotic resistance in fields treated with pesticides. Other research covered by Beyond Pesticides has demonstrated that the resistance develops in the fields. Bacteria have numerous ways of defending themselves that can apply to both pesticides and antibiotics. For example, microbes like Salmonella and E. coli react to glyphosate, dicamba and 2,4-D with a non-specific defense mechanism that enhances their resistance to antibiotics. In fact, antibiotics may be viewed simply as pesticides aimed at microbes rather than fungi, insects, weeds or other pests.
An enormous amount of DNA is available to microbes in their environments, and genes have multiple ways to migrate from one organism to another, either in single-gene units or through mobile genetic elements that provide both genes and the adjunct equipment to function inside a cell. The packet of genes in a bacterium that confers antibiotic resistance is known as the resistome. But little is known about how genes may move through trophic levels from primary producers like bacteria and algae to higher predators.
The current study used a “model food chain†common in soils and frequently used in ecotoxicity studies consisting of Folsomia candida, a very small insect popularly called a springtail, and one of its most common predators, the mite Hypoaspis aculeifer.
The researchers exposed a group of springtails to zinc thiazole, an antibacterial and antifungal chemical, and included a control group of springtails with no exposure. Zinc thiazole has been used in China since the early 2010s, especially against rice pathogens. It is a wide-spectrum treatment and is considered to be of low toxicity, but recently evidence has emerged that it disrupts the thyroid gland. It does not appear to be registered by the U.S. Environmental Protection Agency (EPA) for use in the U.S.
The researchers allowed one group of mites to prey on zinc-thiazole-exposed springtails and another group of mites to prey on unexposed springtails. No mites were directly exposed to the pesticide. Thus, they had two trophic webs, one with pesticide exposure and one without. The researchers then analyzed the gut microbiota of all groups to see if ARGs in the springtails transferred to the mites. They did.
The balance among various microbial species was altered both in the treated springtails versus their control group, and in the mites that ate pesticide-treated springtails compared to the control mites. The mites that preyed on the exposed springtails had different ARGS than those of the control mites, and the treated springtails and their predators shared more ARGs than control springtails and their predators did. This indicated that transfer to the mites from the treated springtails had occurred, showing that pesticide-induced antibiotic resistance can travel not simply among microbes at the same trophic level but up levels via predation.
“The altered and expanded resistomes [resistant genes] of predators suggest that the transmission of ARGs through the soil food chain contributes to resistance spread to higher trophic levels, and our research indicates that this process is amplified under pesticide pressure,†the authors write. “Thus, resistomes may further transfer into higher trophic levels in the food web along with predation and may spread to diverse ecosystems accompanied by invertebrate behavior or activities.â€
Antibiotic resistance is a natural feature of the biosphere because life forms have been attacking and surviving attacks for billions of years. Resistance is transparently Darwinian, whether the struggle has evolved naturally or through human activity—something the pesticide industry has willfully failed to accept since its inception. The pesticide industry’s business model markets toxic substances it knows will generate organism resistance to its chemical and then develop another often more toxic substance, or cocktail of substances, to attack the resistant organism—creating what has been called the pesticide treadmill.
Bacteria are ubiquitous; everything more complex than a microbe has a microbiome, and the current study shows that genes can easily microbiome-hop. The transfer of various resistance mechanisms through microbiomes at different trophic levels is one more consequence of conventional agriculture’s perverse attachment to a delusional idea.
The study result has obvious implications for pesticide usage, because resistance to such chemicals is likely spreading from the lower trophic webs into the microbiomes of organisms like moths and beetles and fungi that attack food crops. Pesticides and antibiotics are altering the structure of entire ecosystems. Their use creates a feedback loop of disaster. It is clear by now that the harmful microbes, like the larger agricultural pests, cannot be completely controlled by pesticides and antibiotics, and the attempt is doing more harm than good over the long term. The insistence that industrial practices can dominate one of the most fundamental of the processes that have created the biosphere—natural selection—is a flawed and dangerous assumption that must change without delay, according to healthy ecosystem advocates.
Organic agriculture supports the biodiversity of soils and preserves the qualities that make them fertile in the first place. See Beyond Pesticides’ 2023 report, Pesticides and You – Beyond Pesticides: Protecting Health and the Environment with Science, Policy, and Action, for a roadmap to transformative change supported by reliable scientific evidence.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
Increased Transmission of Antibiotic Resistance Occurs in a Soil Food Chain under Pesticide Stress
Liu et al.
Ecotoxicology and Public Health December 8, 2024
https://pubs.acs.org/doi/epdf/10.1021/acs.est.4c07822?ref=article_openPDF
Thyroid-disrupting effects and mechanism of thiazole-Zn-induced thyroid cell hypertrophy and hyperplasia in male Sprague-Dawley rats
Honglian et al.
Ecotoxicology and Environmental Safety
Volume 196, 15 June 2020
https://www.sciencedirect.com/science/article/abs/pii/S0147651320303833
FDA Cites Resistance to Medically Important Antimicrobials as Critical Health Issue
Beyond Pesticides, January 11, 2024
https://beyondpesticides.org/dailynewsblog/2024/01/fda-cites-antimicrobial-resistance-as-critical-health-issue/
Glyphosate Induces Antibiotic Resistance in Deadly Hospital-Acquired Infection
Beyond Pesticides, November 8, 2022
https://beyondpesticides.org/dailynewsblog/2022/11/glyphosate-induces-antibiotic-resistance-in-deadly-hospital-acquired-infection/
Antibiotic-Resistance Genes Rise with Pesticide Application, as Study Adds to a Plethora of Findings
Beyond Pesticides, May 29, 2024
https://beyondpesticides.org/dailynewsblog/2024/05/antibiotic-resistance-genes-rise-with-pesticide-application-as-study-adds-to-a-plethora-of-findings/
Widely Used Insecticide Imidacloprid Negatively Impacts Soil Communities, Study Finds
Beyond Pesticides, December 10, 2024
https://beyondpesticides.org/dailynewsblog/category/biodiversity/soil-microbiome/
Pesticides and You Beyond Pesticides: Protecting Health and the Environment with Science, Policy, and Action
Volume 42, Numbers 1–4 & Volume 43, Number 1, 2023
https://www.beyondpesticides.org/assets/media/documents/BP-TransformativeChange.2022.23.pdf
