Plastic Products in Agriculture Pose a Threat of Antibiotic-Resistant Superbugs

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Plastic Products in Agriculture Pose a Threat of Antibiotic-Resistant Superbugs

Plastic Products in Agriculture Pose a Threat of Antibiotic-Resistant Superbugs to Our Food Supply.

Modern agriculture, much like any other industry, heavily relies on plastic. Plastic covers on crop beds, PVC channels for managing field runoff, polyethylene shields in high tunnels, and plastic containers for seeds, fertilizers, and herbicides, among others, are commonplace.

A recent study by researchers from the University of Illinois Urbana-Champaign reveals that these plastics are now widespread in agricultural soil in the form of microplastics and nanoplastics.

Plastic Products in Agriculture Pose a Threat of Antibiotic-Resistant Superbugs

The profound dependence of modern agriculture on plastic has led to the pervasive presence of microplastics and nanoplastics in agricultural soils. Researchers from the University of Illinois Urbana-Champaign warn that these plastics may foster antibiotic-resistant bacteria in our food supply.

This isn’t necessarily a novel revelation; microplastics have been found in nearly all ecosystems and organisms on Earth. The crux of the issue, as emphasized by the researchers from the College of Agricultural, Consumer, and Environmental Sciences (ACES), lies in the possibility that microplastics and nanoplastics in agricultural soil could introduce antibiotic-resistant bacteria into our food supply.

Dr. Jayashree Nath, a postdoctoral researcher in the Department of Food Science and Human Nutrition at ACES and an author of the research report, states, “Plastics themselves may not be inherently toxic, but they can serve as carriers for pathogenic and antibiotic-resistant bacteria to propagate through the food chain. This phenomenon isn’t well-known, and that’s why we aim to raise awareness.”

While the link between microplastics and antibiotic resistance might not be immediately apparent, the mechanism is as follows. Firstly, plastic serves as an excellent adsorbent, meaning chemicals and microorganisms tend to adhere to it. Chemicals that would typically move swiftly through soil, like pesticides and heavy metals, get trapped and concentrated when encountering plastic. Similarly, bacteria and other microorganisms naturally present in the soil tend to aggregate on the stable surfaces of microplastics, forming what’s known as a biofilm.

The presence of microplastic fragments similar to those found in Illinois farmland soil could provide an excellent matrix for pathogenic bacteria to acquire antibiotic resistance and transfer related genes to neighboring bacteria. A new review paper from the University of Illinois calls for more research to clarify the interactions between microplastics and the microbiota in the growing environments of our food. Image Source: Jayita De and Pratik Banerjee, University of Illinois.

When bacteria encounter unusual chemicals in their new abode, they activate stress-response genes to help them resist these substances, sometimes including antibiotics. When groups of bacteria are attached to the same surface, they routinely share these genes through a process known as horizontal gene transfer. Nano-sized plastics that can enter bacterial cells introduce different pressures but yield similar results.

“For millions of years, bacteria have been evolving mechanisms to deal with stress. Plastic is a new material for bacteria in the natural world, so they are now invoking these genetic toolkits to deal with this stress,” explains co-author and Associate Professor of Food Science and Human Nutrition and Illinois Extension Specialist Pratik Banerjee. “We’ve also found that bacteria may become more virulent in the presence of plastic, and their resistance to antibiotics can increase.”

While gene transfer on microplastics has been documented in other environments, especially in water, it’s still a hypothesis in agricultural soils, but that doesn’t mean it’s not happening. Nath and Banerjee are currently conducting laboratory research to document gene transfer.

Banerjee states, “Soil is an understudied area in this field. We have an obligation to understand what’s happening in soil because what we suspect and worry about is that soil might be worse than water. One technical challenge is that soil is a difficult medium for microplastics. Water is easy because you just have to filter out the microplastics.” Banerjee adds, “However, thanks to Jayashree and our collaboration with the Illinois Sustainable Technology Center, we’ve made some good progress.”

The authors note that many foodborne pathogens originate from native soil, but nanoplastics and antibiotic-resistant bacteria could be small enough to enter root systems and plant tissues, where they are unlikely to be washed off. While there is evidence that nanoplastics can enter crops or appear on them, this area of research is still relatively new, and the frequency of such occurrences remains uncertain. Banerjee’s research group also plans to address this question.

In the end, microplastics will continue to persist, as they can endure for centuries or longer in the environment. The authors argue that it’s time to understand their impact on soil and food systems, raise awareness, and promote the development of biodegradable plastic alternatives.