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. Key words: antibacterial activity; clove essential oil (CEO); eugenol; fish pathogenic bacteria; olive flounder PROTIBAKTERIJSKA AKTIVNOST ETERIČNEGA OLJA NAGELJNOVIH ŽBIC IN EVGENOLA PROTI PATOGENIM BAKTERIJAM RIB, IZOLIRANIH IZ GOJENEGA MORSKEGA LISTA (Paralichthys olivaceus) Protibakterijsko delovanje eteričnega olja nageljnovih žbic (Syzygium aromaticum) (CEO) in evgenola je bilo testirano pri sedmih vrstah po Gramu negativnih in devetih vrstah po Gramu pozitivnih patogenih bakterij, ki so bile izolirane iz gojenega morskega lista (Paralichthys olivaceus) v Južni Koreji. Evgenol je bil 99-odstotno koncentriran, CEO pa je sestavljalo sedem kemičnih spojin, med njimi je bilo največ evgenola, ki je predstavljal 83,odstotka eteričnega olja. Metoda difuzije v trdem gojišču, minimalna zaviralna koncentracija (MIC) in minimalna baktericidna koncentracija (MBC) so pokazale, da sta CEO in evgenol zavirala rast tako po Gramu negativnih kot po Gramu pozitivnih bakterij. CEO (MBC/MIC = 1-2) in evgenol (MBC/MIC = 1-4) sta bila baktericidna za vse testirane seve. Odstotek velikosti relativne zaviralne cone je bil visok pri višji koncentraciji CEO in evgenola. Pozitivna soodvisnost je bila opažena med vrednostmi indeksa MAR in vrednostmi MIC pri CEO (r = 0,61) in evgenolu (r = 0,15). Ker sta CEO in evgenol pokazala učinkovito delovanje proti patogenim bakterijam rib, bi bila uporaba CEO in evgenola lahko uporabna za zdravljenje bakterijskih okužb v ribogojništvu. Ključne besede: antibakterijsko delovanje; eterično olje klinčkov (CEO); evgenol; patogene bakterije rib; morski list