The antibacterial activity of lime (Citrus aurantifolia) essential oil (LEO) and limonene was tested against seven Gram-negative and nine Gram-positive fish pathogenic bacteria isolated from cultured olive flounder, Paralichthys olivaceus (Temminck & Schlegel) in Korea. Limonene was >99% concentrated and LEO consisted of eleven chemical compounds including 56.22% of limonene. Disk diffusion assay, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests were done. LEO and limonene inhibited the growth of both Gram-negative and Gram-positive bacteria. LEO and limonene (MBC/MIC= 2-8) were both bactericidal and bacteriostatic for the strains tested. In every fish pathogenic bacteria, the inhibition zone diameter (IZD) increased in proportion to the oil concentration and the maximum effect was found at 100% (V/V) concentrations of LEO and limonene. The antibiogram pattern indicated that all the bacterial strains, excluding three strains of S. iniae (S186, S530, and S131), showed resistance to one or more antibiotics. The percentage of the relative inhibition zone diameter (RIZD %) exhibited high values at higher concentrations of all the agents. Since antibacterial activities of LEO and limonene were considerably effective against fish pathogenic bacteria, they could be used as alternatives to treat bacterial infections in aquaculture.
