Laricrocin92-116 protects Larimichthys crocea against Vibrio parahaemolyticus infection through antibacterial activity, antioxidant effects, and enhanced host immune responses.

Vibrio parahaemolyticus is a halophilic Gram-negative bacterium widely distributed in marine and estuarine environments, and is an important pathogen associated with human and animal infections. The increasing prevalence of antibiotic resistance has prompted the development of alternative antimicrobial strategies. Antimicrobial peptides (AMPs), especially those derived from marine organisms, have attracted increasing attention due to their broad-spectrum activity and low tendency to induce resistance. In this study, a novel AMP, Laricrocin92-116, was identified from the large yellow croaker Larimichthys crocea. Laricrocin92-116 showed broad-spectrum antimicrobial activity, rapid bactericidal kinetics, and excellent stability. In addition, Laricrocin92-116 showed negligible cytotoxicity and hemolytic activity, indicating favorable biosafety. In infected fish models, Laricrocin92-116 significantly improved survival rates. In juvenile large yellow croaker, pretreatment with Laricrocin92-116 markedly reduced bacterial burden and alleviated pathological damage in the intestine and spleen. Furthermore, Laricrocin92-116 modulated the expression of immune-related genes and enhanced antioxidant defenses during infection. Mechanistic studies showed that it disrupted bacterial membrane integrity, induced intracellular oxidative imbalance, inhibited biofilm formation and bacterial motility, thereby impairing bacterial virulence. Collectively, these findings demonstrate that Laricrocin92-116 effectively protects L. crocea against V. parahaemolyticus infection and represents a promising alternative antimicrobial agent for the prevention of vibriosis in aquaculture.