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The antibacterial activities of the rosemary, oregano, clove and cinnamon extracts against Listeria monocytogenes, Bacillus subtilis, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were evaluated in agar diffusion test medium and in sterilized milk medium at 37 °C within 24 hr time interval. All tested herbal extracts exhibited an inhibitory effect against pathogens. Gram-negative bacteria E. coli and P. aeruginosa were less susceptible to the inhibitory activity of all herbal extracts used in the experiment as compared to Gram-positive bacteria Staph. aureus, L. monocytogens and B. subtilis in nutrient agar medium as well as in sterilized milk medium. Oregano showed significant effect against all pathogens as compared to clove, cinnamon and rosemary. Whereas, results from rosemary showed significant decrease inmicrobial activity against pathogens as compared to other tested herbal extracts. These results suggest the prospect of using these herbal extracts in milk and milk products as natural antimicrobials.
Keywords: Antimicrobial activity; Herbs; Pathogens; Sterilize milk