Effect of selected microplastics on the development and spread of antibiotic resistance in bacteria

Microplastics are particles of synthetic and biodegradable polymers with a size of up to 5 mm that have been detected in almost every part of the environment and the food chain. Research has linked microplastics to the dissemination of antibiotic-resistant bacteria in the environment and the food chain. The objectives of this paper were to evaluate the mutagenicity and toxicity of model microplastics to Salmonella enterica subsp. enterica serotype Typhimurium, to evaluate the impact of model microplastics on the emergence and dissemination of antimicrobial resistance to ciprofloxacin in S. Typhimurium, and to assess the behavior of microplastics in contact with different bacteria and DNA. Model microplastics of acrylonitrile butadiene styrene, polylactic acid, polyvinyl chloride, polyethylene terephthalate, a polylactic acid/polyhydroxybutyrate blend, and glitter, as well as their leachates in phosphate buffer or wastewater, had no mutagenic effects on S. Typhimurium TA98 and TA100. Smaller microplastics (0.09-1.25 mm and 0.5 mm in size) had a more pronounced effect on the emergence and development of ciprofloxacin resistance in S. Typhimurium. The highest increase in mutation frequency and mutation rate was observed with polylactic acid microplastics and 7-day glitter leachate. Plasmid DNA containing the ampicillin resistance gene was minimally adsorbed onto microplastics; the highest adsorption rate was observed after 6 h on acrylonitrile butadiene styrene microplastics. The model strain of Pseudomonas aeruginosa and four resistant isolates of Escherichia coli and Staphylococcus aureus formed biofilms on all model microplastics, with the most pronounced biofilm formation observed on polyvinyl chloride microplastics.