Exposure to microplastics reduces the bioaccumulation of sulfamethoxazole but enhances its effects on gut microbiota and the antibiotic resistome of mice

Microplastics (MPs) have aroused a global health concern and their coexistence with antibiotics is inevitable. However, how MPs would affect the bioaccumulation and risks of antibiotics in humans remains poorly understood. Here a mouse model was used, and through dietary exposure, we observed that while the relative distributions of sulfamethoxazole (SMX) in tissues were relatively stable, MPs significantly reduced the bioaccumulation of SMX in mice tissues (liver, lung, spleen, heart and kidney). Notably, while SMX and MPs showed a differential effect, MPs could exacerbate the effects of SMX on gut microbiota and antibiotic resistance gene (ARG) profile, with the relative abundances of sulfonamide resistance genes and multidrug genes being significantly increased. We further identified that shifts in gut microbiota contributed to the changes in ARG profiles in mice. Combined, our results demonstrate that MPs reduced the bioaccumulation of SMX, but they enhanced its effects on gut microbiota and the antibiotic resistome of mice, indicating they might have high risks to humans. [Display omitted] •This is the first report on the effects of MPs on SMX bioaccumulation and their risks in mice.•MPs significantly reduced the bioaccumulation of SMX in mice tissues.•MPs could exacerbate the effects of SMX on gut microbiota and ARG profile.•Combined exposure significantly increased the relative abundances of ARGs.•Shifts in gut microbiota contributed to the changes in ARG profiles in mice.