Carvacrol as a one health-relevant antimicrobial agent: mechanistic insights on its impact on gnotobiotic Artemia and Vibrio campbellii interactions

Introduction: Bacteria belonging to the Harveyi clade of vibrios, including Vibrio campbellii infect many wild and cultured aquatic organisms and cause major losses in global aquaculture. Although not a primary human pathogen, V. campbellii can act opportunistically, particularly following exposure to marine environments or seafood, and in immunocompromised individuals, highlighting the links between aquatic ecosystems, food production systems, and human health. Carvacrol, a phenolic monoterpenoid found in oregano and thyme essential oils, is approved for use in human and animal food. Beyond its safety profile, this compound has also been reported to possess diverse pharmacological effects, including anticarcinogenic, anti-inflammatory and antimicrobial. Methods: Using gnotobiotic brine shrimp Artemia as an in vivo model, we examined whether carvacrol can provide dual protection against V. campbellii by inhibiting the production of bacterial virulence and modulating host immune responses. Results and discussion: Carvacrol significantly improved the survival of Artemia during V. campbellii challenge while showing low toxicity at effective concentrations. The protection was associated with reduced bacterial virulence, including decreased biofilm formation and lower hemolytic and caseinase activities. Additionally, carvacrol modulated the expression of defence-related genes (hsp70, prophenoloxidase, transglutaminase, and ferritin) in time-dependent and stochastic patterns, rather than sustained upregulation. Overall, these findings suggest that carvacrol enhances disease resistance through both pathogen- and host-directed mechanisms. Given its food-grade safety status, carvacrol holds strong translational potential as a functional antimicrobial strategy to support disease control and health management in aquaculture, warranting further evaluation under realistic farming conditions.