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Microplastics boost antibiotic resistance in E. coli, lab study suggests
Co-mingling of tiny pieces of plastic with certain harmful bacteria can make the bacteria harder to fight with several common antibiotics, according to a new study that adds to global concerns about antibiotic resistance.
The study, published Tuesday in the journal Applied and Environmental Microbiology, found that when Escherichia coli (E. coli) MG1655 bacteria, a widely-used laboratory strain, were cultured with microplastics (plastic particles less than 5 millimeters in size), the bacteria became five times more resistant to four common antibiotics than when they were cultivated without the plastic particles.
The findings may be particularly relevant for understanding links between waste management and disease, the study suggests. Municipal wastewater plants contain both microplastics and antibiotics, making them “hot spots” that fuel the spread of antibiotic resistance.
“The fact that there are microplastics all around us …. is a striking part of this observation,” study co-author and Boston University professor Muhammad Zaman said in a press release. “There is certainly a concern that this could present a higher risk in communities that are disadvantaged, and only underscores the need for more vigilance and a deeper insight into [microplastic and bacterial] interactions.”
Many types of bacteria are becoming resistant to antibiotics, largely due to their overuse. Over 2.8 million infections resistant to these medications occur in the US alone each year, killing 35,000 people annually, according to the US Centers for Disease Control and Prevention.
Resistance in E.coli is a concern because even though the bacteria usually live harmlessly in the guts of humans and animals, some strains can cause severe illness. And there are multiple types of dangerous antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), which often causes infections in hospitals, and Clostridium difficile (C.diff), which causes diarrhea.
The new study comes on the heels of another study published in January in the journal Environment International, in which researchers labeled the DNA of bacteria in soil with fluorescent markers to track the spread of genes for antimicrobial resistance, finding that microplastics in the environment boost the spread of resistance by up to 200 times.
The implications of the new study could be important, as part of the evidence of a “strong link” between microplastics and antimicrobial resistance, according to Timothy Walsh, co-founder of the Ineos Oxford Institute for Antimicrobial Research in the UK and an author of the January study.
Walsh said the value of the new study’s findings were limited, however, since the research was conducted in a lab rather in a real-world environment and was focused on just one strain of E.coli.
While scientists are not entirely sure why microplastics may give bacteria an edge against antibiotics, they believe the particles work well as a surface for biofilm, a sticky shield that bacteria form to protect themselves, according to the study. Based on their observations, the new study’s authors concluded that bacteria cells that are better at forming biofilms tend to grow on microplastics, suggesting the plastic particles can “lead to recalcitrant infections in the environment and healthcare setting.”
Microplastics are part of a global plastic pollution crisis, with an estimated 20 million metric tons of plastic waste ending up in the environment each year, according to the International Union for Conservation of Nature.
At the end of 2024, delegates from more than 170 countries met in South Korea after two years of negotiations to finalize a global treaty designed to address the worldwide plastic pollution crisis. However, no treaty was adopted at the session’s close, with plans to reconvene in 2025.
