Selective adsorption of antibiotics on aged microplastics originating from mariculture benefits the colonization of opportunistic pathogenic bacteria

Microplastics and antibiotics widely coexist in the aquatic environment, especially in mariculture regions. However, antibiotics adsorbed on microplastics and their role in the colonization of microorganisms on microplastics are poorly understood. Therefore, in-situ aging experiments were conducted to investigate the impact of antibiotics and microplastics co-occurrence on microorganisms and assess their potential risks to human health. Results showed that antibiotics were adsorbed selectively on microplastics, with 29 investigated antibiotics (n = 40) detected in surrounding water but only 6 investigated antibiotics were adsorbed on microplastics. The concentration of antibiotics accumulated on microplastics was controlled by microplastic types and environmental conditions. For example, aged polypropylene (PP) had more developed pore structures resulting in higher adsorption of antibiotics than other microplastic types. High-throughput sequencing showed higher diversity and distinct composition of microorganisms attached to the microplastics than the surrounding water. Opportunistic pathogenic bacteria such as Mycobacterium possessed positive relationships with tetracycline and doxycycline on aged microplastics, which showed adsorbed antibiotics on aged microplastics could benefit some specific pathogens colonized on the microplastics and spread into unaffected ecosystems, marine organisms even humans. The health risk quotient (HQ) implied the potential human health risk of consuming commercial seafood polluted by antibiotics and microplastic loaded with antibiotics. This study revealed the interaction of antibiotics and microorganisms with aged microplastics in aquaculture systems, providing a novel insight into their synergistic effects on ecological and human health.

Automated summary

Microplastics and antibiotics coexist in the aquatic environment, and the adsorption of antibiotics on microplastics and their impact on microorganisms are poorly understood. This study conducted in-situ aging experiments to investigate the interaction between antibiotics, microplastics, and microorganisms, and assessed the potential risks to human health. The results showed selective adsorption of antibiotics on microplastics, and the concentration of accumulated antibiotics was influenced by the type of microplastics and environmental conditions. High-throughput sequencing revealed a higher diversity of microorganisms attached to the microplastics compared to the surrounding water. Opportunistic pathogenic bacteria were found to have positive relationships with certain antibiotics on aged microplastics, indicating the potential spread of pathogens into unaffected ecosystems and human populations. The health risk quotient (HQ) suggested the potential human health risks of consuming seafood contaminated with antibiotics and microplastics. This study provides valuable insights into the synergistic effects of antibiotics, microplastics, and microorganisms on ecological and human health.