They are everywhere: in oceans, floating in the air, and even inside the human body. Microplastics have become an unavoidable part of modern life. Now, a new study suggests that their presence could be helping bacteria become resistant to life-saving antibiotics.

Researchers at Boston University have found that microplastics (MPs) provide an ideal platform for bacteria to form biofilms—densely packed microbial communities that are more resistant to antibiotics. Their study shows that Escherichia coli bacteria exposed to MPs developed resistance to multiple antibiotics at alarmingly high rates.

Plastic Shields for Superbugs

When the research team, led by Muhammad Zaman, exposed E. coli bacteria to microplastics in the lab, they noticed something unexpected.

“The plastics provide a surface that the bacteria attach to and colonize,” said Neila Gross, a PhD candidate in materials science and engineering at Boston University and lead author of the study.

When bacteria settle on a surface, they build biofilms—slimy, glue-like communities that protect them from outside threats. But on microplastics, these biofilms became particularly resilient. “We found that the biofilms on microplastics, compared to other surfaces like glass, are much stronger and thicker, like a house with a ton of insulation,” Gross explained.

The bacteria thrived, and when antibiotics were introduced, they struggled to penetrate the fortified biofilm.

A New Hotspot for Resistance?

One of the study’s most striking findings was that bacteria that had spent time on microplastics remained highly resistant even after the plastics were removed. This suggests that MPs may select for bacteria with a heightened ability to withstand antibiotics—an alarming scenario given the persistence of microplastics in nature.

The study also found that polystyrene particles facilitated the highest levels of resistance, surpassing both glass and other plastics as a bacterial breeding ground. The team suspects that surface properties, including hydrophobicity (water-repelling) and electrostatic interactions, make certain plastics more favorable for microbial attachment and gene exchange.

For communities already at risk of infectious disease, the findings are especially concerning. “The fact that there are microplastics all around us, and even more so in impoverished places where sanitation may be limited, is a striking part of this observation,” said Zaman a Boston University College of Engineering professor of biomedical engineering who studies antimicrobial resistance.

Refugee settlements, where waste disposal is a challenge and healthcare access is limited, may be particularly vulnerable. Past research has shown that displaced populations face higher risks of antibiotic-resistant infections due to overcrowding and limited medical care. If microplastics are contributing to the spread of these superbugs, the problem could be even worse than previously thought.

“Historically, people have associated antibiotic resistance with patient behavior, like not taking antibiotics as prescribed,” Zaman noted. “But there is nothing a person has done to be forced to live in a particular environment, and the fact is they are at a higher exposure to resistant infections.”

What This Means for Humans

Microplastics are so widespread that they have been detected in clouds, drinking water, and even human blood. They originate from degraded plastic waste, industrial production, and even the synthetic fibers in our clothing.

Yet scientists are still piecing together how they interact with living organisms. Previous research found microplastics can cause bloodclots in mice, as well as inflammation and changes to metabolism. In late 2024, researchers at Penn State University found microplastic fragments can act ice nucleating agents, seeding clouds and thereby altering the atmosphere.

Gross and Zaman hope to expand their research beyond the lab and investigate whether similar resistance patterns emerge in real-world environments.

One key question remains: What exactly about plastic makes bacteria so resilient? One theory is that plastics, which initially repel water, later absorb moisture, potentially soaking up antibiotics before they can reach the bacteria. Even more troubling, the researchers found that bacteria that had grown on plastic retained their strengthened defenses even after the plastic was removed.

Plastics are highly adaptable and their molecular composition could be helping bacteria flourish in ways scientists don’t yet fully understand.

“Too often, these issues are viewed from a lens of politics or international relations or immigration, and all of those are important, but the story that is often missing is the basic science,” Zaman said. “We hope that this paper can get more scientists, engineers, and more researchers to think about these questions.”

The findings appeared in the journal Applied and Environmental Microbiology.