Objective: 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.coliO157:H7 and also determining the period of time needed for bacterial growth initiation is necessary for food safety risk assessment. Method & Materials: This study was designed to model the combined effects of different levels of Bonium Persicum (black cumin) essential oil, temperature, hydrochloric acid and inoculum levels on the growth of E.coliO157:H7 in brain heart infusion broth. Growth was monitored by visible turbidity over 30 days. Results & Conclusion: The measured 108 data points, showed significant effects for selected parameters on growth of E.coliO157:H7. The experiment was carried out in triplicate. For data analysis, SAS statistical software- version 8.2 was employed. Stepwise Multiple Regression Program was used to predict the growth initiation. The model equation was as follows: TTD (Time to Detection) = 29.083 + 4.84 EO – 6.028 pH - 3.90 Temp – 5.33 IL for obtaining a boundary model the logistic Regression Program was used: Y (growth/no growth) = - [6.2218 + (1.89 Eo) - (1.41 Temp) - (2.57 IL) - (2.73 pH)] the models adequately predicted the growth initiation and growth inhibition of E.coli O157:H7.

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