Introduction and Objectives: Escherichia coli O157:H7 is an important human pathogen causing hemorrhagic colitis, hemolytic-ureamic syndrome and thrombotic thrombocytopenic purpura. Knowing the precise boundary for the growth-no growth interface of E.coli O157:H7 and also determining the period of 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 inoculum (103, 105 cfu ml -1) on the growth of E. coli O157:H7 in brain heart infusion broth. Growth was monitored by visible turbidity over a 30 days period. Results: The measured 144 data points, showed significant effects for selected parameters on growth of E.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. Conclusion: The models adequately predicted the growth initiation and growth inhibition of Escherichia coli O157:H7.

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