Epinephrine Enhances Virulence‐Associated Traits of Vibrio alginolyticus and Increases Mortality in Sciaenops ocellatus (Linnaeus, 1766)

ABSTRACT

Stress hormones released during aquaculture handling and environmental disturbances can influence host–pathogen interactions, yet their effects on marine bacterial pathogens remain largely unexplored. This study examined how the stress hormone epinephrine affects the virulence of Vibrio alginolyticus isolated from diseased red drum ( Sciaenops ocellatus ). Ten isolates were exposed to epinephrine concentrations ranging from 0 to 200 µM, and changes in bacterial motility, biofilm formation and extracellular enzyme activities were evaluated. In vivo pathogenicity was assessed by experimentally challenging red drum with epinephrine‐treated and untreated V. alginolyticus strains. Epinephrine exposure significantly enhanced bacterial motility, biofilm formation and the activities of lipase, phospholipase, haemolysin and caseinase ( p  < 0.05). Fish challenged with epinephrine‐treated bacteria exhibited higher cumulative mortality (60%–100%) compared to those exposed to untreated strains (40%–60%). These findings indicate that exposure to epinephrine enhances the virulence of V. alginolyticus , although the underlying regulatory mechanisms remain to be elucidated. This study provides new evidence linking host stress physiology with bacterial pathogenicity in marine aquaculture and underscores the importance of stress management to prevent stress‐associated vibriosis outbreaks.