Protective Effect of Willow ( L.) on Fish Resistance to and .

spp. cause vibriosis in many saltwater and freshwater aquatic species, such as fish, crustaceans, and mollusks. and are among the few species commonly found in infections in fish. This study aimed at investigating the chemical composition and evaluating the antibacterial activities of L. The ethyl acetate (LL2) and methanolic (LL3) extracts were used to evaluate the resistance of strains as LBT6 and VTCC 12233, and two strains of , NG20 and ATCC 17749, and compared their efficacy with cefotaxime in order to find an alternative to antibiotics in the treatment of vibriosis. The obtained results show that the LL2 extract, with its major components identified as chrysoeriol, luteolin, and β-sitosterol, exhibited a bacteriostatic effect against all the tested strains. In parallel, the LL3 extract, with the four major compounds luteolin-7--β-D-glucopyranoside, salicin, p-hydroxy benzoic acid, and β-sitosterol-3--β-D-glucopyranoside, showed significant bactericidal activity against these four strains; the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) varied from 2.0 to 3.0 μg/mL and from 3.5 to 5.0 μg/mL, respectively. Moreover, the LL3 extract could effectively increase the survival rate of the challenged fish at a dose of 5% (/) for the zebrafish () and 3% (/) for the sea bass (. The LL3 extract showed a potential application of L. in the prevention and treatment of vibriosis in fish.