Plastic and Styrofoam products may be contributing to the population’s growing complications of antibiotic resistance bacteria.
Figure 1. Illustration of plastic and microbe products.
Almost everyone has gone to a restaurant or ordered food and received plastic and Styrofoam containers for their takeout. After they no longer have a use, they are discarded, and nothing is thought of the container past the recycling process. However, like many other plastics, these containers experience long-term breakdown processes that produce microplastics. Microplastics are plastic particles within the range of 100nm to 5mm and are frequently found in many ecosystems due to the breakdown of improperly disposed plastic waste (1). These Styrofoam takeout containers are composed of polystyrene polymer plastics and are no exception to this process. The breakdown of these polystyrene materials generates microplastic by-products that tend to find their way into the environment. Microplastics can act as a sink for common chemical contaminants like antibiotics, heavy metals, and bacteria, which has been found to exacerbate their impact.
A recent article published by researchers at Rice University and the University of Houston in the Journal of Hazardous Materials has explored the process these containers follow post-recycling (2). They have found that these microplastics experience Ultraviolet (UV) breakdown from sunlight that generates high surface area platforms allowing for antibiotic resistance gene (ARG) propagation. These antibiotic resistant genes are typically covered by bacterial chromosomes, phages, and plasmids, which all act together to spread antibiotic resistance.
Figure 2. Enhanced ARG horizontal gene transfer from various ARG vectors. Figure taken from reference 2.
These microplastics after UV radiation exposure and breakdown, produce microplastic surfaces with a high propensity to trap susceptible bacteria. This ability to aggregate susceptible bacteria into close sites acts to bring the bacteria into close contact with each other. This acts to accelerate antibiotic resistant gene transfer through proximity effects. At the same time, UV breakdown causes the release of depolymerization by-products from the microplastics that leech into the bacterial membrane. These breach the membrane and act to increase the microbial cell membranes permeability, which promotes easier horizontal gene transfer of ARGs. This synergistic process acts to generate an enriched environment that is favourable for antibiotic resistance, with and without the presence of antibiotics.
The combination of proximal absorption and leaching during microplastic aging in the environment acts synergistically to enrich antibiotic resistance. This highlights the lack of understanding that we have on microplastics in our environment, and the marked public health and environmental impact that they may have. This study warrants future research to identify other polymeric materials and their breakdown products, and the effects they may have. Current plastic products produced by the materials world have their unique benefits in structural properties but need replacements to prevent their long-term effects. An obvious first step would be to limit our consumption of these single-use products, but this still does not stop their eventual collection. Hopefully in the near future, regulations will focus on the banning of these materials and replacement with more environmentally friendly products that give the same consumer benefits we desire, while limiting their long-term impact.
The findings of this research has been published in the Journal of Hazardous Materials:
Yuan, Q.; Sun, R.; Yu, P.; Cheng, Y.; Wu, W.; Bao, J.; Alvarez, P. J. J. UV-Aging of Microplastics Increases Proximal ARG Donor-Recipient Adsorption and Leaching of Chemicals That Synergistically Enhance Antibiotic Resistance Propagation. J. Hazard. Mater. 2021. DOI: https://doi.org/10.1016/j.jhazmat.2021.127895.
References:
1) Microplastic pollution aids antibiotic resistance. https://phys.org/news/2021-12-microplastic-pollution-aids-antibiotic-resistance.html (accessed Dec 10, 2021).
2) Yuan, Q.; Sun, R.; Yu, P.; Cheng, Y.; Wu, W.; Bao, J.; Alvarez, P. J. J. UV-Aging of Microplastics Increases Proximal ARG Donor-Recipient Adsorption and Leaching of Chemicals That Synergistically Enhance Antibiotic Resistance Propagation. J. Hazard.
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