Harmful bacteria can survive on plastic waste washed up on beaches

Harmful bacteria on sewage-related plastic waste washed up on beaches can survive long enough to pose a risk to human health, according to new research.

The University of Stirling team found ‘concentrated reservoirs’ of faecal bacteria still present on litter such as wet wipes and cotton swabs on beaches in Scotland.

Led by Professor Richard Quilliam, the team discovered that bacteria such as E.coli and intestinal enterococci (IE) bind to these plastics more often than to natural materials such as seaweed and sand, prolonging their persistence in water and on the beach.

“We all know that sewage waste on our beaches is unsightly, but it could also be a public health risk,” Prof Quilliam said.

Much has been said recently about direct discharges of wastewater into rivers and the sea, especially after heavy rains when some treatment plants exceed their effective treatment capacity.

Bags of plastic waste collected

“Some of the plastic waste we recovered could have come from sewage spills that have lingered in the environment, but the volume of waste we are seeing is shocking,” Prof Quilliam said.

His team collected plastic waste from ten beaches along the Firth of Forth estuary in Scotland, including bathing beaches like Aberdour Silver Sands and Portobello. “We expected to collect a few wet wipes everywhere, but the team came back with bags,” he said.

PhD researcher Rebecca Metcalf, also from the University of Stirling, is the lead author of a new paper reporting the study. She said: ‘Finding faecal bacteria could also point to the possibility of other human pathogens such as norovirus, rotavirus or salmonella.

“The extent to which people might be exposed to these pathogens is beyond the scope of our study, but there is obviously always a risk of children picking up and playing with wet wipes or other plastic waste on the beach.”

Antimicrobial resistance

The team also found evidence that species of vibrio – a naturally occurring bacterium, some strains of which can cause severe stomach upset – were able to colonize the wet wipes. And they found high rates of antimicrobial resistance – resistance to antibiotics – present in the bacteria on the wipes and cotton swabs.

The research is part of the £1.85million ‘Plastic Vectors’ project – funded by the Natural Environment Research Council (NERC) – which studies how plastics in the environment can help carry bacteria and viruses, and the impact it can have on human health.

Reference: Metcalf R, White HL, Moresco V, Ormsby MJ, Oliver DM, Quilliam RS. Sewage-related plastic waste washed up on beaches can act as a reservoir of fecal bacteria, potential human pathogens, and antimicrobial resistance genes. Mar. Pollute. Bull. 2022;180:113766. doi: 10.1016/j.marpolbul.2022.113766

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Bryce K. Locke