Chemical composition and antimicrobial activity of Achillea wilhelmsii C. Koch essential oil against selected bacterial and fungal pathogens isolated fish

Background & Aim: Increasing resistance of fish pathogens to chemical drugs, using herbal plants with antimicrobial properties is necessary. In this study, the chemical composition and antimicrobial activity against bacterial and fungal pathogens isolated from fish of the essential oil from the aerial parts of Achillea wilhelmsii C. Koch growing wild (Southwest of Iran) were studied. Experimental: The aerial parts of A. wilhelmsii were tested against five bacterial strains including, Streptococcus iniae, Yersinia ruckeri, Vibrio angularum, Aeromonas hydrophila and Pseudomonas aeruginosa and four pathogenic fungi, Saprolegnia sp., Fusarium solani, Candida albicans and Aspergillus flavus. The oil constituents of A. wilhelmsii were analyzed by GC/MS. Results & Discussion: The major composition of the essential oil of A. wilhelmsii were 1.8-cineole (25.2%), camphor (18.9%), linalool (6.9%), borneol (5.7%) and artemisia alcohol (4.3%). All microorganisms showed more sensitivity to essential oil of A. wilhelmsii than the control antibiotics. The highest antimicrobial activity were observed against Y. ruckeri (25.4 mm) and C. albicans (25 mm), respectively, while S. iniae (16.4 mm) and A. flavus (14 mm) exhibited the least sensitivity. In addition, MIC test indicated that minimum concentrations of the essential oil ranged from 125 to 800 μg/L were able to inhibit the growth of the selected bacterial and fungal pathogens. Industrial and practical recommendations: Results indicated that the essential oil of A. wilhelmsii could be a potential source of new and effective antibacterial components in aquaculture industry. Although, more study needed to purify, fractional and characterize various antimicrobial compounds from the essential oil of A. wilhelmsii.