Investigating Antibacterial Effect of Thyme (Thymus persicus) and Pennyroyal (Mentha longifolia) Alcoholic and Aqueous Extracts against Isolated Bacteria from Domestic Cheeses

Background & Objective: Food poisonings caused by consumption of domestic dairy products such as cheese due to Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) are one of the hygienic problems in foodstuffs. Nowadays, using natural preservatives instead of synthetic preservatives in foods has been regarded increasingly and among these natural compounds, medicinal plants comprise these materials that finding their antimicrobial effects have high priority. The aim of this study was to investigate antibacterial effect of Thyme (Thymus persicus (and Pennyroyal (Mentha longifolia) alcoholic (ethanolic) and aqueous extracts against isolated bacteria from domestic cheeses. Material & Methods: After preparing Thyme and Pennyroyal, alcoholic (ethanolic) and aqueous, the extract of these plants were gained and their antimicrobial effects were investigated in concentrative levels of 0.39- 100 percent against E. coli and S. aureus isolated from domestic cheese by microdilution method. E. coli PTCC 1270 and S. aureus PTCC 1112 were used as control. Results: Alcoholic (ethanolic) extract of Thyme and Pennyroyal showed more antibacterial effect against Staphylococcus aureus in comparison with Escherichia coli (P<0.05). Thyme ethanolic extract showed more antibacterial effect than Pennyroyal ethanolic extract (P<0.05). Aqueous extract of Thyme and Pennyroyal did not show any significant antibacterial effect in tested concentration (P>0.05). Conclusion: According to current study results, alcoholic (ethanolic) extract of Thyme and Pennyroyal have high antibacterial potency and they can be used as alternative instead of synthetic preservatives for protection against food borne bacterial poisoning and infection.