In vitro and in vivo antibacterial activity of essential oils against Vibrio scophthalmi isolated from farmed turbot Scophthalmus maxius

Abstract:

[Objective] To evaluate the antibacterial activity of essential oils against Vibrio scophthalmi HZ-C1 isolated from farmed turbot Scophthalmus maxius in vitro and in vivo. [Methods] The paper disc diffusion method and microbroth dilution technique were employed to determine the antibacterial activity of 14 essential oils. Cell membrane disruption induced by Litsea cubeba oil was examined by transmission electron microscopy (TEM), and by measuring the release of intracellular lactate dehydrogenase (LDH) and 260 nm absorbing material. Meanwhile, antibacterial activity of Litsea cubeba oil in vivo was investigated using a turbot model of vibriosis by intraperitoneal injection. [Results] The 14 essential oils showed different antibacterial activities against V. scophthalmi HZ-C1, and cinnamaldehyde had the highest activity with a minimum inhibitory concentration (MIC) of 0.25 μL/mL, followed by thymol, eugenol, citral and Litsea cubeba oil with a MIC of 0.5 μL/mL. Litsea cubeba oil can disrupt the plasma membrane of V. scophthalmi HZ-C1 and cause the leakage of protease and nucleic acid. After immersing in a bath containing 200 μL/L Litsea cubeba oil, the mortality of turbots infected by V. scophthalmi was reduced from 50% to 0. [Conclusion] Essential oils rich in aromatic aldehyde, phenolic compounds and citral show high antibacterial activities against V. scophthalmi HZ-C1, and thus have the potential to replace the use of antibiotics for treating vibriosis in farmed turbot.