Antibacterial activity and mechanism of sanguinarine against Vibrio parahaemolyticus

Sanguinarine (SE), a benzophenanthridine alkaloid derived from Macleaya cordata, represents a promising antibiotic alternative in aquaculture; however, its antibacterial mechanism against the economically important pathogen Vibrio parahaemolyticus remains poorly understood. This study investigated the antibacterial activity and mechanism of SE against V. parahaemolyticus through integrated phenotypic and transcriptomic approaches. In vitro assays showed that SE exhibited potent antibacterial activity with a minimum inhibitory concentration (MIC) of 62.5. Phenotypic analyses revealed that SE disrupted cell membrane integrity of V. parahaemolyticus, as evidenced by ultrastructural damage and increased membrane permeability, and significantly inhibited biofilm formation and bacterial motility (swimming and swarming) at sub-inhibitory concentrations. In an in vivo challenge trial in Macrobrachium rosenbergii, dietary supplementation with SE (0.5 and 1.0 g/kg feed) significantly reduced bacterial load in the hepatopancreas and increased survival rates, while also mitigating hepatopancreas histopathological damage. Transcriptome analysis identified 1,657 differentially expressed genes, with significant downregulation of the two-component system and key metabolic pathways such as the citrate cycle (TCA), oxidative phosphorylation, and fatty acid degradation. These findings demonstrate that SE exerts antibacterial effects through multi-target mechanisms involving membrane disruption, virulence attenuation, and energy metabolism interference, highlighting its potential as a sustainable agent for controlling V. parahaemolyticus infections in aquaculture.