Pathogens love to sit on plastic

A whole host of bacteria travel on plastic waste in river water, including pathogens: microorganisms that can make people sick. Many are also resistant to some antibiotics that are important in fighting diseases. Plastic pollution thus poses a health risk from an unexpected angle: not only because of the plastic itself and the materials contained in it, but also as a potential source of infection and a reservoir of antibiotic resistance. Which Write British, Canadian and Spanish researchers this week Microbiological nature.

The fact that many microorganisms live on plastic is not new. Scientists even talk about a separate ecological niche: the so-called plasticosphere, where unique micro-communities flourish. Until now, most research has focused on the so-called “plastic soup” found in the sea. But major rivers around the world also make up a plastic soup: they transport several thousand tons of plastic into the sea every year. This concerns not only visible waste, but also micro- and nano-plastics.

Biofilm

Researchers conducted experiments in Britain’s River Sway. The plastic they stuck in the river was covered within a week with so-called biofilms: a layer of bacteria, fungi and viruses. It is clear that the composition of this biofilm differs from that of pieces of wood that have remained in river water for a week, and from microorganisms that live loosely in river water. In particular, partially decomposed plastic contains a relatively large number of pathogens, including: Pseudomonas aeruginosa, the notorious hospital bacteria. The bacteria on this weathered plastic also contain a relatively large number of genes that code for antibiotic resistance.

“These results do not surprise me,” answers Anna Maria de Rhoda Hausmann, a microbiologist at RIVM and professor of global changes and environmentally transmitted infectious diseases at Utrecht University. She did not participate in the investigation Microbiological natureBut it is self-published with colleagues Similar research In 2021. The researchers did not look at the materials they suspended in the river themselves, but at plastics of all sizes that they sieved from the water. “The result was fairly similar,” she says. “It is interesting to see this now confirmed in this experimental design.”

Survival

De Rhoda Hausmann explains that the interaction between plastics and pathogens is important: “Plastic affects the way pathogens move in the environment. If microorganisms attach to heavy particles, they can sink to the bottom, preventing them from spreading further. But if They stick to molecules that float well, so they can spread better.

She stresses that scientists are conducting research on this matter, because there is a constant exchange of microorganisms between nature and our human environment. “Many of the bacteria that cause disease do not survive easily in the environment, but perhaps more easily in these plastics,” says De Rhoda-Hausmann. “They can end up back to us via different routes, for example if people swallow water while swimming.” The bacteria and their resistance to antibiotics can then spread further among people.

It’s still not clear why disease-causing bacteria like to attach themselves so much to plastic, preferably weathered plastic, according to the article published in the journal. Microbiological nature. Researchers speculate that organic materials may leach from plastics used as food. RIVM’s De Rhoda Hausmann suspects that the porous material simply provides an attractive surface for bonding.

resistance

RIVM conducts research in plastics in a large consortium including Utrecht University, Deltares, TNO and the University of Twente. “All kinds of things are happening in this plastic soup, in the microbiological realm,” says de Rhoda-Hausmann. “This may also include new populations of bacteria and resistance that are relevant to public health.”

The microbiologist does not yet dare say to what extent river plastics actually pose a danger in this regard. “We have to investigate it further.”