Pal Amit, Labuza Theodore P, Diez-Gonzalez Francisco
Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, MN 55108, USA.
Food Microbiol. 2008 May;25(3):460-70. doi: 10.1016/j.fm.2008.01.009. Epub 2008 Feb 2.
This study compared the performance of four primary mathematical models to study the growth kinetics of Listeria monocytogenes ribotypes grown at low temperature so as to identify the best predictive model. The parameters of the best-fitting model were used to select the fastest growing strains with the shortest lag time and greatest growth rate. Nineteen food, human and animal L. monocytogenes isolates with distinct ribotype were grown at 4, 8, and 12 degrees C in tryptic soy broth and slurries prepared from cooked uncured sliced turkey breasts (with or without potassium lactate and sodium diacetate, PL/SD) and cooked cured frankfurters (with or without PL/SD). Separate regressions were performed on semi-logarithm growth curves to fit linear (based on Monod) and non-linear (Gompertz, Baranyi-Roberts, and Logistic) equations and performance of each model was evaluated using an F-test. No significant differences were found in the performance of linear and non-linear models, but the Baranyi model had the best fit for most growth curves. The maximum growth rate (MGR) of Listeria strains increased with the temperature. Similarly MGR was found significantly greater when no antimicrobials were present in the formulation of turkey or frankfurter products. The variability in lag times and MGRs in all media as determined by the Baranyi model was not consistent among strains. No single strain consistently had the fastest growth (shortest lag time, fastest MGR, or shortest time to increase 100-fold), but nine strains were identified as fastest growing strains under most growth conditions. The lack of association between serotype and fastest strain was also observed in the slurry media study. The fastest growing strains resulting from this study can be recommended for future use in L. monocytogenes challenge studies in delicatessen meat and poultry food matrices, so as to develop conservative pathogen growth predictions.
本研究比较了四种主要数学模型在研究低温下生长的单核细胞增生李斯特菌核糖型生长动力学方面的性能，以确定最佳预测模型。使用最佳拟合模型的参数来选择具有最短延迟时间和最大生长速率的生长最快的菌株。19株具有不同核糖型的食品、人类和动物单核细胞增生李斯特菌分离株，在胰蛋白胨大豆肉汤以及由未腌制熟切片火鸡胸肉（添加或不添加乳酸钾和双乙酸钠，PL/SD）和熟腌制法兰克福香肠（添加或不添加PL/SD）制备的浆液中，于4、8和12摄氏度下培养。对半对数生长曲线进行单独回归，以拟合线性（基于莫诺德方程）和非线性（冈珀茨方程、巴拉尼 - 罗伯茨方程和逻辑斯蒂方程）方程，并使用F检验评估每个模型的性能。线性和非线性模型的性能未发现显著差异，但巴拉尼模型对大多数生长曲线的拟合效果最佳。李斯特菌菌株的最大生长速率（MGR）随温度升高而增加。同样，当火鸡或法兰克福香肠产品配方中不存在抗菌剂时，发现MGR显著更高。由巴拉尼模型确定的所有培养基中延迟时间和MGR的变异性在菌株之间不一致。没有单一菌株始终具有最快的生长速度（最短的延迟时间、最快 的MGR或增加100倍所需的最短时间），但在大多数生长条件下，有9株菌株被鉴定为生长最快的菌株。在浆液培养基研究中也观察到血清型与最快生长菌株之间缺乏关联。本研究中产生的生长最快的菌株可推荐用于未来在熟食肉类和禽肉食品基质中进行的单核细胞增生李斯特菌挑战研究，以便制定保守的病原体生长预测。
