The Trojan Horse Effect of Microplastics: Mediating <i>Aeromonas Hydrophila</i> Transmission and Synergistic Pathogenesis in <i>Micropterus Salmoides</i>

Microplastics (MPs) are prevalent in aquatic environments, ingested by aquatic organisms, causing substantial impacts on major physiological functions, while their surfaces facilitate microbial colonization. However, the effect of MPs in facilitating pathogenic transmission, which is highly susceptible to serving as potential vectors for contaminants and pathogens, is not fully understood. This study investigated the synergistic effect of polystyrene microplastics (PS-MPs) as a pathogen vector in mediating <i>Aeromonas hydrophila</i> transmission. Electron microscopy revealed that PS-MPs can act as a carrier for <i>A. hydrophila</i>, significantly enhancing the bacterial infection in <i>Micropterus salmoides</i>, inducing a higher mortality rate and severe inflammatory infiltration in hepatic tissue, and disrupting the activities of antioxidant enzymes and the expression of related genes. These findings provide the first report of the mechanism underlying PS-MPs-mediated synergistic transmission of <i>A. hydrophila</i> in <i>M. salmoides</i>, establishing a crucial theoretical basis for the risk assessment of MPs pollution and for the control of aquaculture diseases.