The antibacterial activity of essential oil of oregano (Origanum vulgare L.)

Antibacterial activities of the essential oil of oregano (Origanum vulgare L.) and ampicillin on Escherichia coli RSKK 340, Klebsiella pneumoniae RSKK 06017, Pseudomonas aeruginosa RSKK 06021, Salmonella enteritidis RSKK 96046, Streptococcus pyogones RSKK 413/214, Bacillus cereus RSKK 1122, Staphylococcus aureus RSKK 96090 and methicilline-resistant Staphylococcus aureus (MRSA) were determined. The minimum inhibitory concentration (MIC) for oregano oil against various bacteria varied: while M.luteus (16 μg/ml) and B.cereus (32 μg/ml) were susceptible to oregano oil, the others exhibited partly resistance. Except MRSA S. aureus (250 μg/ml), ampicillin had more effect on K. pneumoniae (128 μg/ml) and C. albicans (128 μg/ml) than oregano oil, but very low concentrations of the essential oil were sufficient to prevent microbial growth. Of the bacteria tested, Micrococcus luteus and Bacillus cereus proved to be most susceptible to oregano oil. Oregano oil possessed strong antimicrobial activity compared with the antibiotic. Gram-positive bacteria were more sensitive to the antimicrobial agent in spice than Gram-negative ones.