Antibacterial effects of some medicinal plant essential oils against Lactococcus garvieae, Yersinia ruckeri and Aeromonas hydrophila

In this study, the antibacterial effects of essential oil extracted from 4 medicinal plants, (Thymus deansis, Satureja bachtiarica, Cuminus cyminam and Myrtus communis) carvacrol, tymol, florfenicol and tetracycline against three pathogenic bacteria (Aeromonas hydrophila, Yersinia ruckeri and Lactococcus garvieae) were evaluated. Minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) of the essential oils were evaluated after preparation of serial dilution. Inhibition zone were also determined on Muller Hinton agar medium. According to the results, the largest inhibition zone was observed from S. bachtiarica and C. cyminam essential oils against A. hydrophila, Y. ruckeri and L. garvieae. The obtained results showed different MICs and MBCs for different bacteria; however, in most cases the essential oils were more effective than tetracycline. Tymol, florfenicol and S. bachtiarica essential oil demonstrated the highest inhibitory and bactericidal effects against A. hydrophila, Y. ruckeri and L. garvieae, respectively. The MIC and MBC of tymol against A. hydrophila were 6.3 and 12.5 μg ml-1, respectively. The MIC and MBC of florfenicol against L. garvieae were 3.125 and 6.25 and of S. bachtiarica essential oil against Y. ruckeri were 6.25 and 12.5 μg ml-1, respectively. It can be concluded that the sensitivity of the bacteria studied to the essential oils are different. However, considering the antimicrobial effects of some essential oils, it is necessary to evaluate their beneficial effects in prevention and treatment of bacterial diseases in fish.