Microplastics in the environment can increase the spread of antimicrobial resistance (AMR) by up to 200 times, according to research carried out at the UK’s Ineos Oxford Institute for Antimicrobial Research and Fujian Agriculture and Forestry University, China.
Publishing their work in Environment International, the researchers explain that the degradation of plastic waste to smaller particles allows them to absorb pollutants such as antibiotics, heavy metals and potential and potential bacterial pathogens. In addition, recent investigation suggests that microplastics can also provide a unique adhesive platform allowing bacteria to colonise the surface. Microplastics in the environment therefore act as a platform for bacteria to attach and exchange genes with their neighbours via plasmids, a process known as horizontal gene transfer.
The researchers assert that the presence of microplastics in the horizontal gene transfer process increases the frequency of plasmid conjugation, and the movement of plasmids carrying antibiotics resistant genes between bacteria up to 200 times, compared to control samples with no microplastics.
“Antimicrobial resistance and environmental degradation are existential global health threats. This link between microplastics and AMR is particularly concerning as microplastics pollution will have significant ramifications on controlling the spread of AMR,” said Professor Timothy Walsh, Director of Biology, Ineos Oxford Institute for antimicrobial research and co-author of the paper.
Using a newly developed culture-independent conjugation method, the researchers investigated how four microplastics - polyethylene, polypropylene, polystyrene and polystyrene terephthalate - at different size and concentrations found in the environment, promote transfer of plasmids. The results showed that DNA exchange between bacteria was promoted in the presence of microplastics by triggering stress-related pathways in the bacteria.
“These findings definitively link two global health emergencies - AMR and environmental degradation via microplastics. Given the lack of global plastic waste governance and the increasing amount of microplastics ubiquitously infiltrating all aspects of human activity, these finding are very concerning,” Walsh added.
The researchers highlight that by 2050 at least ten million people each year will die from AMR, costing the global economy at least $100 trillion. Most of this impact is expected to be felt by low-middle income countries. In addition, there is limited understanding of how climate change and environmental degradation relates to AMR.
With some 20 million metric tons of meso-, macro- and micro-plastics leaking into the environment every year, and an environmental half-life that can persist for decades, microplastics act as long-term stimulants for the spread of AMR.
This research comes as negotiations on a global plastics treaty are set to continue. A final treaty was due to be completed at negotiations held in Busan, Korea the end of 2024.
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