Does microplastic promote the spread of antibiotic-resistant microorganisms?

The World Health Organization (WHO) describes antibiotic resistance as one of the most serious threats to public health. In 2019, more than 550,000 deaths in Europe have been linked to bacterial antimicrobial resistance, and more than 130,000 deaths have been directly attributed by doctors to antibiotic resistance. How can we counter this alarming phenomenon?

Antibiotic resistance vs. microplastics

The seven main pathogens linked to the acquisition and transmission of antibiotic resistance genes are Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecium, Streptococcus pneumoniae and Acinetobacter baumannii. Researchers estimate that antimicrobial resistance could cause as many as 10 million deaths per year by 2050 [1].

The problem of antibiotic resistance is also strongly associated with environmental pollution and the presence of plastic waste in the environment, especially micro- and nanoplastics [1, 2]. When microplastics enter the natural environment, they react with various specific components of their microhabitat, including chemical compounds present in drugs [3]. In addition, the surface hydrophobicity of microplastics promotes the formation of biofilms, which intensify the accumulation of organic contaminants and mediate chemosensory reactions, thus altering the sorption capacity of microplastics [4, 5].

For example, in a study using norfloxacin (an antibiotic commonly used to treat urinary tract, gastrointestinal tract, respiratory tract and skin and soft tissue infections), the sorption efficiency of the antibiotic on microplastics made of PVC, or poly(vinyl chloride), increased by more than 50 percent. – Half as much antibiotic could be accumulated on the microplastics, forming hot spots with elevated concentrations of contaminants [5]. Biofilms have been shown to promote the adsorption behavior of plastic particles, affecting their physical and chemical properties [5].

The role of biofilms

Biofilm formation is a dynamic process in which adherent microorganisms secrete a so-called extracellular polymeric substance. The growth of biofilms results in the production of polysaccharides and lipids, which interfere with the chemical structures of microplastics, increasing their degradation and releasing the production compounds they contain, such as plasticizers [6]. It has been confirmed that microplastic biofilms exhibit different properties compared to biofilms overgrowing non-plastic surfaces, especially in marine, river and lake environments.

Studies show that these communities are less diverse in terms of taxa, but often contain specific types of bacteria, such as Pseudomonas, that can degrade plastics [5]. The process of biofilm formation is affected by many factors, such as temperature, insolation, and oxygen content. In addition, in real systems there is a peculiar cocktail of contaminants – chemical compounds and microplastics of different sizes and made of different polymers, which makes it difficult to predict the ultimate effects of these combinations [6]. So far, it has been confirmed that biofilms present on microplastics can enrich antibiotics on their surface from the surrounding water, which in turn promotes the transfer and acquisition of antibiotic resistance genes by microorganisms present in biofilms [7].

Effects of microplastics on microorganisms

In a study, the results of which were published in early March 2025 in the journal Applied and Environmental Microbiology [8], researchers examined how Escherichia coli bacteria reacted to different concentrations and types of microplastic, but in the presence of common antibiotics – ampicillin, ciprofloxacin, doxycycline and streptomycin. The results are worrisome because bacteria exposed to microplastic under laboratory conditions have become resistant to many types of antibiotics commonly used to treat infections – they have acquired multidrug resistance. The biofilm, in which the microorganisms clustered, provided a kind of shield of protection against adverse factors, including subsequent doses of antibiotics [8].

It was shown that the resistance rate of biofilms formed on microplastics was 5 to 75 times higher compared to other materials. And the bacteria themselves isolated from microplastics tended to form stronger biofilms for several more days after leaving the surface of plastics. Although studies on the effect of microplastics on the growth of antibiotic-resistant microorganisms have appeared a lot in recent years [2], researchers first pointed out the impaired motility of microbes, the cause of which can be traced precisely to plastics [8]. In the presence of low concentrations of antibiotics, there is a combinatorial effect between the selection of antibiotic-resistant genes and the formation of biofilms, which amplifies the occurrence of the phenomenon. The most important factors on the part of microplastics and biofilms contributing to antibiotic resistance are shown in Figure 1.

Biofilms undoubtedly play a key role in the spread of antibiotic resistance genes. Bacteria in biofilms produce persister cells that are metabolically inert, which is one mechanism for avoiding antibiotics. Biofilms act as a refuge for plasmids [8]. In addition, the extracellular polymeric substance that shields microorganisms contains numerous negatively charged functional groups (e.g., carboxyl, hydroxyl and phosphate). These provide sites for adsorption of contaminants from the environment and free genes.

However, research has largely focused on the role of bacteria in biofilms, overlooking the complex plastisphere structures that are present in real environments. In natural environments, algae may play a dominant role, controlling the composition of the bacterial community in biofilms. Antibiotic resistance genes in the phytosphere or surrounding environments can interact with specific species, can be transported over long distances due to the unique carrying capacity of microplastics, or can end up in animal and human organisms, undergoing further transformations and entering into new interactions [9].

How to counteract the rise of antibiotic resistance?

We must remember that the problem of antibiotic resistance consists of many factors, including the overuse and misuse of antibiotics, as well as poor sanitation and hygiene (lack of access to water and sanitation services) and increasing pressure from climate change.

Edyta Łaskawiec, Ph.D. – water and wastewater technologist, science popularizer, author of an educational profile on Instagram platform: wastewater_based.doctor and the podcast About Wastewater. Winner of the POP SCIENCE Competition for Science Popularizers of the Silesian Science Festival Katowice 2024. Eco-educator in the project “Social Activity Laboratory – Urban Lab 5D in Gliwice”.

In the article, I used, among others:

[1] European Antimicrobial Resistance Collaborators, The burden of bacterial antimicrobial resistance in the WHO European region in 2019: a cross-country systematic analysis, Lancet Public Health, Vol. 7 2022, 897-913.

[2] Liu Y., et al, Microplastics are a hotspot for antibiotic resistance genes: Progress and perspective, Science of The Total Environment, Vol. 773, 2021, 145643.

[3] Syranidou E., Kalogerakis N., Interactions of microplastics, antibiotics and antibiotic resistant genes within WWTPs, Science of The Total Environment, Vol. 804, 2022, 150141.

[4] Li Y-Q., Zhang Ch-M., Yuan Q-Q., Wu K., New insight into the effect of microplastics on antibiotic resistance and bacterial community of biofilm, Chemosphere, Vol. 335, 2023, 139151.

[5] Nguyen H.T., et al, Microplastic biofilms in water treatment systems: Fate and risks of pathogenic bacteria, antibiotic-resistant bacteria, and antibiotic resistance genes, Science of The Total Environment, Vol. 892, 2023, 164523.

[6] Zheng Z., et al, Interaction between microplastic biofilm formation and antibiotics: Effect of microplastic biofilm and its driving mechanisms on antibiotic resistance gene, Journal of Hazardous Materials, Vol. 459, 2023, 132099.

[7] Jia J., et al, Biofilm formation on microplastics and interactions with antibiotics, antibiotic resistance genes and pathogens in aquatic environment, Eco-Environment & Health, 2024, Vol. 3, Issue 4, 516-528.

[8] Gross N., et al, Effects of microplastic concentration, composition, and size on Escherichia coli biofilm-associated antimicrobial resistance, Environmental Microbiology, 2025: https://doi.org/10.1128/aem.02282-24

[9] Yu X., et al, Microplastics exacerbate co-occurrence and horizontal transfer of antibiotic resistance genes, Journal of Hazardous Materials, Vol. 451, 2023, 131130.