Isoborneol as a natural food-grade antimicrobial: Targeting biofilm resilience of Vibrio alginolyticus on seafood and contact material surfaces.

Vibrio alginolyticus is an emerging seafood-borne pathogen with a high ability to form biofilms on seafood and food-contact surfaces, causing persistent contamination and higher tolerance to sanitation. Here, we evaluate the antibacterial, antibiofilm and anti-virulence potential of isoborneol, a natural food-grade monoterpenoid, against V. alginolyticus in this study. Isoborneol consistently demonstrated antibacterial activity against V. alginolyticus, with minimum inhibitory concentration and minimum bactericidal concentration values of 500 μg/mL. Membrane permeability, nucleic acid leakage, extracellular protein release, extracellular ATP leakage and scanning electron microscopy collectively supported membrane impairment as an important factor in the antibacterial activity of isoborneol. Isoborneol also effectively reduced mature biofilm, metabolic activity and cell viability in a dose dependent manner. It inhibited immature biofilm formation, extracellular polymeric substance production, cell surface hydrophobicity, auto-aggregation, swimming and swarming motilities and selectively modulated the expression of genes involved in quorum-sensing, biofilm formation, flagellar motility, type IV pili, and outer membrane functions. Isoborneol inhibited bacterial adhesion, invasion and V. alginolyticus induced cytotoxicity in Caco-2 cells with no detectable cytotoxicity at the tested sub-MIC concentrations. Moreover, isoborneol has a strong capacity to destroy mature biofilms of V. alginolyticus on the surface of stainless-steel coupons and shrimp shells. The viable cell-counts, survival, metabolic activity and biofilm structural integrity were reduced without visibly damaging the surface of the shrimp shell. Altogether, these findings provide a framework for isoborneol to be considered as a potential natural antibacterial and antibiofilm agent against V. alginolyticus. However, additional safety, sensory, and industrial evaluations are essential before practical application.