Plastics in rivers: a breeding ground for pathogens

River water can contain pathogens and antibiotic resistance genes housed in the plastic waste that reaches its riverbeds.

An international study published in the scientific journal Microbiome led by Joseph Cristi-Oleza of the Department of Biology of the University of the Balearic Islands, shows that microbial communities that grow in plastic waste from rivers can contain harmful microorganisms and act as a reservoir of antibiotic resistance genes.

Pathogen study procedure

Scientists characterized microbial communities found on plastic surfaces soaked for seven days in the Sawe River (United Kingdom), one kilometer from a wastewater treatment plant, in February 2020 and from rivers in Spain, France and Portugal.

The samples were analyzed using a variety of techniques, including DNA sequencing, bacterial culture and antibiotic resistance assays.

Microbial communities on new and old plastic were compared with those found on control surfaces (wood) and in river water.

The types of harmful microorganisms extracted from plastic samples
and wood differed from those in the river water samples

The authors found that the plastic, wood and water samples contained potentially pathogenic bacteria, but the types of harmful microorganisms detected in the plastic and wood samples were different from those in the river water samples.

"Opportunistic" bacteria

The plastic and wood samples contained potential pathogens such as Pseudomonas aeruginosa, Acinetobacter and Aeromonas, known "opportunistic" bacteria that pose a greater risk to people with weakened immune systems, while the water samples contained others latent in humans such as Escherichia, Salmonella, Klebsiella and Streptococcus.

The authors highlight the importance of monitoring wastewater discharges 
due to its risks to human health and the environment

The authors also found that although the microorganisms recovered from all samples contained antibiotic resistance genes, which could be transferred to other bacteria, which could contribute to the development of antibiotic resistance in humans and animals, the types of resistance They varied between the plastic, wood and water samples.

When the authors compared the microbial communities growing on new and old plastic, they found that P.
(which can cause infections in hospitalized patients) was especially abundant in samples of degraded plastic.

They speculate that this may be because degraded plastic releases more organic compounds that support microbial growth than new plastic.

They also found that the relative abundance of antibiotic resistance genes present in the microbial community was higher in old plastic samples than in new plastic samples, although they noted that the reason is still unclear.

What steps to take

The authors believe that more research is needed into the potential risk of plastic pollution due to its ability to store and transport potentially pathogenic bacteria and antibiotic resistance genes.

They also emphasized the importance of monitoring wastewater discharges due to the risks they pose to human health and the environment.

These findings could help inform policies and practices aimed at reduce plastic pollution in the rivers.

The study is a reminder of the dangers of pollution by this material and invites us to reflect on measures to eliminate them that could include reducing the use of single-use plastics, improving their management and cleaning rivers of plastic waste. .


Zadjelovic, V., et al. "Microbial hitchhikers harboring antimicrobial-resistance genes in the riverine plastisphere." microbiome (2023)

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