Application of probabilistic model to calculate probabilities of escherichia coli O157:H7 growth on polyethylene cutting board

Abstract

This study calculated kinetic parameters of Escherichia coli O157:H7 and developed a probabilistic model to estimate growth probabilities of E. coli O157:H7 on polyethylene cutting boards as a function of temperature and time. The surfaces of polyethylene coupons (3×5 cm) were inoculated with E. coli O157:H7 NCCP11142 at 4 Log CFU/cm2. The coupons were stored at 13 to 35°C for 12 h, and cell counts of E. coli O157:H7 were enumerated on McConkey II with sorbitol agar every 2 h. Kinetic parameters (maximum specific growth rate, Log CFU/cm2/h; lag phase duration, h; lower asymptote, Log CFU/cm2; upper asymptote, Log CFU/cm2) were calculated with the modified Gompertz model. Of 56 combinations (temperature×time), the combinations that had ≥0.5 Log CFU/cm2 of bacterial growth were designated with the value of 1, and the combinations that had increases of <0.5 Log CFU/cm2 were given the value 0. These growth response data were fitted to the logistic regression to develop the model predicting probabilities of E. coli O157:H7 growth. Specific growth rate and growth data showed that E. coli O157:H7 cells were grown at 28-35°C, but there were no obvious growth of the pathogen below 25°C. Moreover, the developed probabilistic model showed acceptable performance to calculate growth probability of E. coli O157:H7. Therefore, the results should be useful in determining upper limits of working temperature and time, inhibiting E. coli O157:H7 growth on polyethylene cutting board.