Science: Study Shows that Microplastic Exposure Heightens Microbial Virulence

This article is from Hakai Magazine, an online publication that explores the relationship between science and society in coastal ecosystems. Discover more insightful stories like this at hakaimagazine.com.

A new concern has emerged from the combination of two 20th-century challenges to public and environmental health: microplastics and antimicrobial resistance.

The ocean is home to countless microorganisms, as well as plastic since the mid-20th century. Scientists have previously found that plastic serves as a habitat and transportation system for marine microbes, including potentially harmful human pathogens. Recently, a team led by microbiologist Sasha Tetu from Macquarie University in Australia discovered that chemicals leaching from microplastic pollution can alter microbial communities, making them more virulent and increasing antimicrobial resistance.

Tetu and her colleagues conducted their research in a lab setting, mixing seawater samples with polyvinyl chloride (PVC) leachates and monitoring changes in the DNA of the water’s bacteria over six days.

PVC is one of the most common plastics and, like many others, it releases additives such as metals, dyes, and stabilizers that enhance its performance.

The researchers are still uncertain about the exact mechanisms at play, but they observed that bacteria exposed to plastic increasingly carried genes associated with higher virulence and antimicrobial resistance.

Further analysis revealed a more complex pattern, instead of a general increase in resistance to all antimicrobials. The bacteria showed a higher abundance of genes that resist certain classes of antimicrobials, while the prevalence of genes that protect against other groups of antibiotics decreased.

Additionally, the prevalence of genes related to specific types of virulence, such as mechanisms to suppress a host’s immune response, significantly increased, while genes linked to other harmful activities decreased.

Although many of the genes for antimicrobial resistance were identified in non-human pathogenic bacteria, this does not eliminate the potential risk to human health. Tetu explains, “Microbes have many different ways of sharing genes, often across distantly related lineages.”

Tetu emphasizes that her research is a starting point, and more investigation is necessary to understand how plastic leachates impact microbial communities. However, the general finding is that plastic exposure promotes the proliferation of more resilient microbes with increased antimicrobial resistance, an unintended consequence.

Emily Stevenson, a graduate student at the University of Exeter in England, studies how microplastics affect the spread of antimicrobial-resistant bacteria. She commends this new research for addressing important questions about the influence of plastic exposure on microbial communities. The extent to which the lab findings apply to real-world conditions remains uncertain, but Stevenson expresses concern.

“What worries me,” she says, “is the potential antimicrobial properties of these leachates themselves.” Many plastics contain known antimicrobials, such as triclosan. Stevenson points out, “If those substances are available to bacteria, they could create selective pressure leading to the evolution of antimicrobial resistance.”

This article is from Hakai Magazine, an online publication that explores the relationship between science and society in coastal ecosystems. Discover more insightful stories like this at hakaimagazine.com.

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