Characterization and tolerance of foodborne pathogenic bacteria in microplastic biofilm

Microplastics have the ability to selectively accumulate microorganisms from their surrounding environments, leading to the formation of biofilms. The potential for microplastic biofilm in food processing environments to contaminate the processing environment and food matrices poses a threat to food safety. This study validated the biofilm formation of three commonly encountered foodborne pathogens, Salmonella enterica serovar Typhimurium (ST), Staphylococcus aureus (SA), and Listeria monocytogenes (LM) on microplastics, and investigated their tolerance to disinfectant and gastrointestinal tract. Three strains showed distinct biofilm formation patterns, with biomass reaching a steady state at 2 d. Meanwhile, the particle size of microplastics exhibited a specific impact on biofilm formation, with smaller microplastics sizes leading to increased biofilm formation. Sodium hypochlorite (NaClO) can effectively eliminate most biofilm-forming bacteria, except for ST. After treatment with 50 ppm NaClO, 34% cells in ST biofilm survived. Only SA survived in simulated gastric fluid, with around 3 log reduction after 1 h. ST and LM were not detected. All three strains showed a slight increase after treatment with simulated intestinal fluid for 6 h. These results highlighted the capacity of microplastics to transport pathogens through biofilms, emphasizing the potential synergistic effects between microplastics and pathogens in food-associated environments.