Comparison between Two Groups of Pathogenic Bacteria under Different Essential Oil Extract of Ocimum basilicum L.

This study was conducted to assessment the antibacterial activities of different part of basil essential oil on the standard gram-negative bacteria include Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and gram-positive ones including Bacillus cereus, Staphylococcus aureus, and Listeria monocytogen. The basil essential oil was provided from two part of the plant (leaf and herb) at the two different developmental stages. The antibacterial properties of basil essential oil was studied on the standard bacteria by agar disk diffusion, then minimal inhibition concentration (MIC) and minimum bactericidal concentration (MBC) were detected. The results of agar disk diffusion tests showed the inhibition zones as follow: Listeria monocytogen۱۷.۱۱-۱۷.۴۲ mm, St. aureus ۲۹.۲۰-۳۰.۵۶ mm, B. cereus ۱۴.۷۳-۱۶.۰۶ mm, E. coli ۲۱.۶۰-۲۳.۵۸ mm, Salmonella typhi ۲۱.۶۳-۲۴.۸۰ mm and for P. aeruginosa the maximum inhibition zones were observed on leaf essential oil. From the herb part of basil almost similar results were obtained: Listeria monocytogen ۱۷.۰۲-۱۷.۶۷ mm, St. aureus ۲۹.۶۰-۳۰.۴۱ mm, B. cereus ۱۰.۶۶-۱۶.۱۱ mm, E. coli ۱۷.۴۸-۲۳.۵۴ mm, Salmonella typhi ۲۱.۵۸-۲۱.۶۴ mm and for P. aeruginosa the maximum inhibition zones were observed. The MICs for gram-positive bacteria were as: B. cereus ranging ۳۶-۱۸ μg/mL, S. aureus ۱۸ μg/mL, Listeria monocytogen ۱۸-۳۶ μg/mL and for gram-negative bacteria of E. coli, Salmonella typhi and P. aeruginosa were ۱۸-۹ μg/mL. Some of basil oil component increased by water stress. Amount of the main constituents of the oil such as linalool, methyl chavicol, ۱,۸–cineole and trans α-bergamotene significantly affected by water stress.