Global Veterinaria 9 (1): 73-79, 2012 ISSN 1992-6197 © IDOSI Publications, 2012 DOI: 10.5829/idosi.gv.2012.9.1.6426 Corresponding Author: Azadeh Mahmoodi, Department of Fisheries, Science and Research Branch, Islamic Azad University, Tehran, Iran. 73 Chemical Composition and Antibacterial Activity of Essential Oils and Extracts from Rosmarinus officinalis, Zataria multiflora, Anethum graveolens and Eucalyptus globulus Azadeh Mahmoodi, Laleh Roomiani, Mehdi Soltani, 1 2 3 Afshin Akhondzadeh Basti, Aboulghasem Kamali and Shahroz Taheri 4 1 5 Department of Fisheries, Science and Research Branch, Islamic Azad University, Tehran, Iran 1 Department of Fisheries, Islamic Azad University, Abadan Branch, Abadan, Iran 2 Department of Aquatic Animal Health, Faculty of Veterinary Medicine University of Tehran,Tehran, Iran 3 Department of Food Hygiene, Faculty of Veterinary Medicine University of Tehran,Tehran, Iran 4 Islamic Azad University, Shoushtar Branch, Iran 5 Abstract: The objective of the study was to characterize the chemical constituents and antibacterial properties of Rosmarinus officinalis(rosemary), Zataria multiflora (oregano), Anethum graveolens (Dill) and Eucalyptus globulus (Eucalyptus) essential oils (EO) and extracts against Lactococcus garvieae. Lactococcosis is one of the infectious diseases with significant economic and sanitary repercussions for trout farms in Iran during the summer months. Four EOs were initially screened against Lactococus garvieae using agar disc diffusion and broth dilution methods. The highest efficacy against the tested strain was shown when testing the Orogano EO. The chemical components of selected EOs were also analyzed by GC/MS. The most important constituents of the Rosemary, Oregano, Dilland Eucalyptus were 1,8-cineole (78.6 %), carvacrol (71.1 %), D-carvacrol (36.09 %) and 1,8-eucalypol (72.71 %), respectively. Of the 4 plants tested, Z.multiflora essential oil was the most active showing a Minimum Inhibitory Concentration (MIC) of 7.8 µg/mL and a Minimum Bactericidal Concentration (MBC) of 15.6 µg/mL. The diameters of the zone of inhibition adjacent to essential oils were estimated 24, 32, 18.5 and 16 mm, respectively. The extracts of different plant resulted in variable zone of inhibition (28–14.8 mm) for L.garvieae. The research results showed that the essential oil from of Z.multiflora has a great potential for application as a natural antimicrobial agent to preserve food. Key words: Lactococcus garvieae Antibacterial activity Foodborne pathogens Minimum Inhibitory Concentration (MIC) Minimum Bactericidal Concentration (MBC) INTRODUCTION in food. Aromatic plants have been used traditionally Today’s there is a significant consumer demand for Plants contain extensive variety of phytochemical foods that are minimally processed and free from compounds with antimicrobial activity [2]. The Clove, synthetic chemical preservatives with the perception of Cinnamon, Oregano, Rosemary and Dill are considered being ‘‘natural”. As a result the food industry is facing as the most common spices and herbs with strong great challenges to produce naturally occurring food antimicrobial activity. Their essential oils containing antimicrobials and antioxidants to reduce the use of chemical compounds such as Carvacrol, Cinnamaldhyde, synthetic chemical preservatives and still produce safe Eugenol and Camphor are identified as the major foods that are also regarded as healthy. Also, there are chemical components responsible for exerting increasing trends to use herbal life style and dietary antimicrobial activity [3]. They are used as culinary choices for human welfare and to improve the herb a beverage drink as well as cosmetics. In folk productivity and health of farm animals these natural medicine it is used as analgesic, antirheumatict, products can help the whole body and improve the carminative, diuretic, expectorant, anti-epileptic, anti immunological status [1]. Spices and herbs are well spasmodic in renal colic, improve human fertility and known for their antimicrobial and antioxidant properties stimulate hair growth. Also some of this material added and have the ability to produce multidimensional flavors as an antioxidant to food [4]. in the therapy of some diseases for a long time. Many