New research from Plymouth Marine Laboratory shows that pathogenic and antimicrobial-resistant bacteria colonise microplastics in the natural environment.
Microplastics are plastic particles less than 5mm in size and are extremely widespread pollutants.
It is estimated that over 125 trillion particles have accumulated in the ocean (from the surface to the seabed), and they have also been detected in soils, rivers, lakes, animals, and the human body.
An emerging concern associated with these substrates is the microbial communities that rapidly establish on particle surfaces, forming complex biofilms known as the ‘plastisphere’. These communities may often include pathogenic (disease-causing) or antimicrobial-resistant (AMR) bacteria.
Therefore, the researchers have called for urgent action for waste management and strongly recommend wearing gloves when partaking in any beach cleans.
The role of wastewater in spreading antimicrobial-resistant bacteria
Wastewater treatment plants or solid waste landfill sites have been proposed to spread, boost, or influence the evolution of antimicrobial resistance and pathogens in nature.
This could increase the risk to human health, meaning it’s vital that more is understood about the interactions between bacterial communities within the plastisphere and other marine pollutants, such as domestic and clinical wastewater.
Lab studies have shown that some commonly discarded plastic materials serve as platforms for the selective growth of bacterial communities responsible for AMR and diseases in both humans and animals.
Whilst previous work has explored this in the environment, several questions and issues remained unanswered, which this new study aimed to address.
Dr Emily Stevenson, lead author and PhD researcher with Plymouth Marine Laboratory, explained: “Following the recent concerning release of sewage bio-beads in Sussex, this timely study highlights the pathogenic and AMR risk posed by microplastic substrates littering our ocean and coasts.
“By identifying high-risk substrates, we can improve the monitoring of those, or even phase them out for safer alternatives.”
Harmful bacteria found in UK waterways
The research team developed a novel structure that would allow five different substrates (bio-beads, nurdles, polystyrene, wood, and glass) to be secured along a waterway, thereby reducing anthropogenic pollution downstream.
After two months in the water, bacterial biofilms growing on each substrate were analysed using metagenomics, the genomic analysis of genetic material collected from an entire community of organisms in a specific environment.
- Pathogens and AMR bacteria were found on all substrates, across all sample sites.
- Polystyrene and nurdles may pose a greater AMR risk than other substrates, potentially due to their ability to adsorb antibiotics and promote biofilm formation that facilitates transfer of antimicrobial resistance genes (ARGs).
- Over 100 unique ARG sequences were identified in microplastic biofilms, which is more than on natural (wood) or inert (glass) substrates.
- Environmental bio-beads can support bacteria that carry resistance genes to key antibiotics, like aminoglycosides, macrolides, and tetracyclines.
- Unexpectedly, some bacterial pathogens increased in prevalence moving downstream when associated with microplastic biofilms.
- Environmental location played a significant role in microbial community composition and AMR gene prevalence.
- There is a potential biosecurity risk posed by microplastics, particularly in areas near aquaculture facilities, where filter-feeding organisms may ingest colonised particles containing pathogens and ARGs.
More effective waste management is essential
Dr Stevenson commented: “As this work highlights the diverse and sometimes harmful bacteria that grow on plastic in the environment, we recommend that any beach cleaning volunteer should wear gloves during clean-ups, and always wash their hands afterwards.”
The researchers emphasised the need for further research into how microplastics interact with co-occurring pollutants, and for improved waste-management practices to reduce the spread of AMR and pathogenic organisms in the environment.
