Tabriz University of Medical Sciences Pharmaceutical Sciences 1735-403X 19 2 2013 09 01 Determination of Antimicrobial Effects of Nisin and Mentha spicata Essential Oil against Escherichia coli O157:H7 Under Various Conditions (pH, Temperature and NaCl Concentration) 61 67 EN Mir-Hassan Moosavy Nassim Shavisi Journal Article 2013 12 16 Plant essential oils and nisin have been known as antimicrobial agents that could be used to control food-borne pathogenic bacteria such as Escherichia coli O157:H7. The aim of this study was to evaluate the antimicrobial efficacies of nisin and Mentha spicata essential oil (EO) both separately and in combination, against Escherichia coli O157:H7 at different temperatures (4, 9 and 14°C), pH (5, 6 and 7) and NaCl concentrations (0, 1, 2 and 4%). Methods: The chemical components of EO were analysed by GC-MS. The minimum inhibitory concentrations (MIC) of nisin and EO were assessed using a broth micro-dilution method. For combinations of the antimicrobials, the Differences in Population assay were used to determinate their effects. Results: The dominant active components of EO were carvone (78.76%) and limonene (11.50%). The EO MIC value was 40µl/ml, but nisin did not inhibit the growth of E.coli O157:H7. The susceptibility of E.coli O157:H7 to nisin and EO was found to enhance with increasing incubation temperature, pH and NaCl concentration. Conclusion: Our findings demonstrate that a combination of nisin and Mentha spicata essential oil might be a potential source of preservative for the control of E.coli O157:H7 in the food industry