Background: In order to reduce or eliminate foodborne pathogens or food spoilage agents many research have been done to find natural preservatives.

Objective: This study was carried out to determine minimum inhibitory concentration (MIC) of lysozyme and zataria multiflora Boiss. essential oil on E. coli O157: H7 and their sub inhibitory concentration effect on bacterial growth curve.

Methods: In this study different concentrations of lysozyme (0. 125, 250, 500 and 1000 µg/ml) and zataria multiflora Boiss. essential oil (0, 0.005, 0.01, 0.02, 0.04 and 0.08%) were used alone and in combination on BHI broth to determine MIC of zataria multiflora Boiss. essential oil and lysozyme with macro dilution and micro dilution methods and effect of sub inhibitory concentrations of them on bacterial growth curve of E. coli O157: H7.

Results: MIC of essential oil in two methods was achieved 0.04% whereas lysozyme in 1000 µg/ml concentration was not able to reduce bacterial growth. Furthermore combination results revealed that high concentration of lysozyme was not able to reduce calculated amount of MIC of essential oil. Sub inhibitory concentration effect of EO and lysozyme showed that their combination result in the increase of lag phase and reduction of bacterial growth.