Don’t trash it! Plastic junk is making microbes more resistant to antibiotics

Next time you’re about to throw out that Styrofoam container from last night’s takeout, just think that it could turn into a breeding ground for antibiotic-resistant bacteria. 

Polystyrene (the fancier name for Styrofoam) waste which gets broken down into microplastics provides a haven for microbes to multiply. The stuff gets worse the more it breaks down. Floating genetic material can power them up with antibiotic-resistant genes (ARGs), made up of all sorts of nasty bio-weapons like phages, plasmids, and chromosomes, vectors that can make even powerful antibiotics ineffective. No defense against bacteria can mean lethal infections.

Something else that might make you think twice about polystyrene is the chemicals that escape it as it degrades. These can help the vectors transfer genetic material that can boost a bacterium’s ability to fight off antibiotics. Researcher Pingfeng Yu of Zhejiang University in China, part of a team of scientists from Rice University and other institutions, recently coauthored a study on this disturbing process in Journal of Hazardous Materials.

“Microplastics are made of polymers, and ultraviolet exposure can oxidize these polymers during ultraviolet aging,” Yu told SYFY WIRE. “Aging increases the microplastic surface area and enhances its affinity to AGR vectors such as antibiotic resistant bacteria, phages, and extracellular ARGs.”

UV radiation isn’t hard to find on Earth. When it hits microplastics, it breaks polymer chains and produces free radicals — another thing you definitely don’t want floating around. Free radicals have such an awful reputation in skincare because they are thought to be behind some visible signs of aging. These unstable atoms can do serious damage to other human cells, causing much more severe problems than a few wrinkles. If an atom’s outer shell is missing electrons, it can bond with another atom to get an electron refill, becoming a free radical.

It doesn't help that polystyrene also releases chemicals as it breaks down. Toxins like serene and benzene (both of which are possible carcinogens) can leach out of the coffee cup you just tossed in the trash and help vectors with the horizontal transfer of antibiotic-resistant genes. Horizontal gene transfer (HGT) happens when genetic information is passed on from one organism to another. Transferred genes and the pathogens that receive them keep evolving, which can create a super-bacteria that is no longer affected by the antibiotics meant to kill it off. 

“HGT includes conjugation (such as bacteria-bacteria transfer), transduction (like phage-bacteria transfer) and transformation (free DNA-bacteria transfer),” said Yu. “Leaching chemicals can induce oxidative stress in the recipient bacteria and make the bacterial surface more permeable.”

About those chemicals, they don’t need to wait for an accumulation of bacteria to be destructive. They were probably leaching into the coffee you were drinking from that cup before it ended up in a landfill somewhere. These chemicals can strengthen microbes’ resistance to antibiotics by breaking through the membranes of the bacteria, giving dangerous ARGs the opportunity to creep in. As more bacteria breed on the same surface, they come into closer contact with each other and the resistance-enhancing chemicals. Yu is concerned. 

“These genes encode enzymes that degrade antibiotics,” he said. "Once they are introduced into new host bacteria through biological vectors, the new host may harbor these genes and express the according enzymes.”

Don’t be fooled by the recycling symbol on Styrofoam containers, either. Polystyrene can be remade into things such as packing peanuts but isn’t really recyclable. Just avoid it like the plague that it could bring on if we aren’t careful.