Purpose: This study described a kinetic behavior of E. coliO 157:H7 and developed probabilistic model to calculate growth probabilities of the pathogen on cutting boards.
Methods: E. coli O157:H7 (4 log CFU/cm2) was inoculated on polyethylene coupons (3 × 5 cm). The inoculated coupons were stored at 13, 15, 20, 25, 28, 30, 33 and 35 °C for 12 h, and E. coli O157:H7 cell counts were enumerated on McConkeyII with sorbitol agar every 2 h. Kinetic parameters (max: growth rate (log CFU/cm2/h), LPD: lag phase duration (h), and Nmax: upper asymptote (log CFU/cm2) were calculated with the modified Gompertz equation. The 0.5-log CFU/cm2 was used as a threshold to determine growth or no growth for 56 combinations (8 temperatures, 7 sampling times). The growth response data were analyzed with the logistic regression analysis to produce growth/no growth interfaces at 0.1, 0.5, and 0.9 of probabilities. The model performance was then validated with observed data.
Results: Obvious growth of E. coli O157:H7 on coupons were not observed during storage at 12, 15, 20 and even at 25 °C for 12 h, but cell counts of the pathogen increased (P < 0.05) at 28, 30, 33 and 35 °C with 4.31-7.20 h of LPD, 0.42-2.06 log CFU/cm2/h of max, and 5.7-7.1 log CFU/cm2 of Nmax, depending on temperatures. Growth/no growth boundaries of E. coli O157:H7 were produced at 0.1, 0.5 and 0.9 of probabilities with acceptable performance (concordance: 99.3 %, discordance: 0.6 %). In addition, validation for the developed model was acceptable.
Significance: These results should be useful in determining working temperature and time not to allow E. coli O157:H7 growth on cutting boards.