BACKGROUND: There is growing evidence that resistance to antibiotics is increasing, and because of their wide range of negative impacts on the environment and humans, also accumulative effects in fish meat and hazards for humans, there have been numerous studies conducted using medicinal plants as a healthier alternative to antibiotics.OBJECTIVES: This study examined the antibacterial effect of two native medicinal herbs (oregano and echinacea mixed essential oil) on Lactococcus garvieae compared with some commercial antibiotics used in fish farms.METHODS: The antibacterial activities against a fish bacterial pathogen (Lactococcus garvieae) were tested using the disk diffusion method, followed by the determination of minimum inhibitory (MIC) and bactericidal (MBC) concentrations via sequential dilution of essential oil by Broth Micro Dilution method.RESULTS: The results showed antimicrobial activities of mentioned mixed essential oil with MIC ≥ 6.25 μL/mL and MBC ≥ 12.5 μL/mL. Also, the measurements of the diameter of inhibitory zones are consistent with the results of MIC and MBC, indicating the positive effect of this plant mix oil Lactococcus garvieae. However, the Lactococcus garvieae was more sensitive to Enrofloxacin (NFX 5), and Sulfamethoxazole &amp; Trimethoprim (SXT) (P<0.05), but the combination of Oregano and Echinacea essential oils performed better than Florfenicol (FF) despite the weaker effects against mentioned two antibiotics.CONCLUSIONS: The results approved the antibacterial activity of the mixed essential oil of oregano and Echinacea against Lactococcus garvieae on the laboratory scale. Using these compounds as a possible substitute for antibiotic compounds requires more clinical studies.

BACKGROUND: It is fundamental to find the safest food preservatives in order to acheive the maximum health and economic benefits. Salmonella enteritidis is the cause of Salmonellosis, one of the most important foodborn zoonoses in poultry. OBJECTIVES: The present study was conducted to comparatively evaluate the antimicrobial effects of Trachyspermum copticum, Thymus vulgaris, and Cinnamomum zeylanicum essential oils and Formaldehyde against Salmonella Enteritidis. METHODS: In this study minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Cinnamomum zeylanicum, Trachyspermum copticum, and Thymus vulgaris essential oils against Salmonella enteritidis were determined using broth macro-dilution. The effects of essential oils on growth curve of Salmonella Enteritidis were also evaluated. RESULTS: In this study, MIC for the minimum inhibitory concentration level of Trachyspermum copticum, Thymus vulgaris, Cinnamomum zeylanicum and formaldehyde for Salmonella Enteritidis was determined as 500, 700, 500, and 70 ppm while MBC was calculated as 700, 900, 1000, and 200ppm, respectively. This study revealed that all the treatments increased lag phase. Bacterial growth speed was slower for Trachyspermum copticum of all the concentrations, yet a significant difference was observed only in 1 and 2 MIC of other treatments (p < /em><0.05). CONCLUSIONS: In conclusion, Trachyspermum copticum (with less concentration), Thymus vulgaris, and Cinnamomum zeylanicum (with higher concentration) could be employed as a substitution of a proporation of formaldehyde to prevent bacterial development in food.