Antibacterial activity of clove essential oil and eugenol against fish pathogenic bacteria isolated from cultured olive flounder (Paralichthys olivaceus)

Abstract

The antibacterial activity of clove (Syzygium aromaticum) essential oil (CEO) and eugenol was tested against seven Gram-negative and nine Gram-positive fish pathogenic bacteria isolated from cultured olive flounder (Paralichthys olivaceus) in Korea. Eugenol was >99% concentrated and CEO consisted of seven chemical compounds including 83.63% of eugenol. Disk diffusion assay, MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) tests showed CEO and eugenol inhibited the growth of both Gram-negative and Gram-positive bacteria. CEO (MBC/MIC= 1-2) and eugenol (MBC/MIC= 1-4) were bactericidal for all tested strains. The percentage of relative inhibition zone diameter exhibited high values at higher concentration of both CEO and eugenol. Positive correlation was observed between MAR index values and MIC values of CEO (r =0.61) and eugenol (r =0.15). Since antibacterial activity of CEO and eugenol were effective against fish pathogenic bacteria, the use of CEO and eugenol could be advantageous to treat bacterial infections in aquaculture.