Objective: Escherichia coli O157:H7 is an important human pathogen causing hemorrhagic colitis, hemolytic –uremic syndrome and thrombotic thrombocytopenia purpura. Knowing the precise boundary for the growth-no-growth interface of Escherichia coli O157:H7 and also determining the period of the time needed for bacterial growth initiation is necessary for food safety risk assessment. Materials and Methods: this study was designed to examine the combined effects of different levels of carum copticum (zenyan) essential oil (0%, 0.015%, 0.03%, 0.06%) , temperature (35 C, 25 C), pH (5,6,7) and inoculums (103 , 105cfu ml-1) on the growth of Escherichia coli O157:H7 in brain heart infusion broth. Growth was monitored by visible turbidity over a 30 days period. Results and Conclusion: the measured 144 data points, showed significant effects for selected parameters on growth of Escherichia coli O157:H7 (p<0.05). The experiment was carried out in triplicate. Stepwise Multiple Regression Program was used to predict the growth initiation. For obtaining a boundary model the logistic regression program was used. The models adequately predicted the growth initiation and growth inhibition of Escherichia coli O157:H7.

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