A new study conducted by researchers at the University of Illinois Urbana-Champaign found that the presence of microplastics increases the virulence of foodborne Salmonella and encourages biofilm formation.

The study was overseen by Pratik Banerjee, Ph.D., Associate Professor of Food Safety and Associate Head for Graduate Programs in the University of Illinois Department of Food Science and Human Nutrition within the College of Agricultural, Consumer, and Environmental Sciences. The lead author of the study was Jayita De, a graduate student in Dr. Banerjee’s lab. Their findings were published in the Journal of Hazardous Materials.

Nanoplastics Affect Salmonella Virulence, Biofilm Formation, AMR

The researchers examined the time- and concentration-dependent effects of polystyrene nanoplastics on Salmonella enterica at low, moderate, and high levels of exposure ranging from 2.5–100 milligrams per liter (mg/L).

Under realistic conditions, the researchers observed upregulation of Salmonella virulence genes when first introduced to nanoplastics. Over time, Salmonella increased biofilm formation, but when introduced to greater concentrations of nanoplastics, Salmonella started to become more virulent once again. The researchers described the phenomenon as a “trade-off between offense and defense,” as extended or high-dose exposure suppresses key factors of pathogenicity, reflecting cellular fatigue, toxicity overload, and trade-offs that favor survival over virulence.

Concerningly, the researchers also found that the presence of nanoplastics can exacerbate antimicrobial resistance (AMR) in Salmonella. Although not antimicrobials, exposure to nanoplastics may trigger the expression of AMR genes that have cross-resistance to actual antibiotics.

Microplastics Affect E. coli Similarly

Dr. Banerjee’s team previously studied the effects of nanoplastics on Escherichia coli O157:H7, finding that nanoplastics can influence the growth, viability, virulence, physiological stress response, and biofilm formation of the foodborne pathogen.

Similar research conducted by Boston University has also suggested that microplastics could be contributing to increased AMR and enhanced biofilm formation capabilities in E. coli.

Is Plastic Food Packaging a Concern?

Dr. Banerjee and his team were inspired to investigate the interaction between plastic particles and Salmonella after frequently detecting the pathogen in retail turkey samples collected during previous research, given that ground turkey is often packaged in plastic.

Despite his findings that nanoplastics can affect the behavior of Salmonella, Dr. Banerjee explained that further research is needed to determine the actual impact of these changes before raising concerns.

“We don’t want to sound the alarm and advocate that people stop using plastics,” Dr. Banerjee said. “Plastic packaging provides a lot of benefits, such as reducing food spoilage and waste while keeping expenses low. We don’t know yet whether this is something we should be worried about.”