A Survey of Antibacterial Effects of Oliveria decumbens and Nepeta binaludensis Essential Oils on Staphylococcus aureus and Escherichia coli in Doogh

Plant extracts and essential oils are commonly used in traditional and industrial doogh products to inhibit bacterial activities. In this study, the antibacterial effects of the essential oils of Olivera decumbens and Nepeta binaludensis against Staphylococcus aureus and Escherichia coli in doogh were investigated. Essential oils of Olivera decumbens and Nepeta binaludensis were collected from Binalud and Pol-Dokhtar respectively and the essential oil of these species were extracted by the hydro-distillation method. Then, different concentrations of essential oils (12.5, 50, 100 and 200 μl mL-1) were added to doogh containing 104 Staphylococcus aureus and Escherichia coli bacteria. Finally, the bacteria were counted during 5 days of storage. The results showed that, at the maximum duration of 5 days storage, the difference between the inhibitory activity of Oliveria decumbens and Nepeta binaludensis essential oils at concentrations of 50 and 100 μl mL-1 respectively against Escherichia coli and Staphylococcus aureus in comparison with control sample was significant (P < 0.05). Moreover, it was observed that the antibacterial effect of Oliveria decumbens was higher than Nepeta binaludensis due to its more phenolic compounds. The results of the present study have shown that essential oils of Oliveria decumbens and Nepeta binaludensis have good inhibitory effects against Staphylococcus aureus and Escherichia coli in doogh. So they can be used as preservatives in traditional and industrial doogh products.