Growth of Escherichia coli O157:H7 in raw ground beef stored at 10 degrees C and the influence of competitive bacterial flora, strain variation, and fat level.
Growth of Escherichia coli O157:H7 in raw ground beef stored at 10 degrees C and the influence of competitive bacterial flora, strain variation, and fat level.
复制标题
大肠杆菌 O157:H7 在 10°C 储存的生碎牛肉中的生长以及竞争性菌群、菌株变异和脂肪水平的影响。
DOI：
10.4315/0362-028x-65.10.1535
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发表时间：
2002
影响因子：
2
通讯作者：
M. Tamplin
中科院分区：
文献类型：
--
作者：
M. Tamplin
基于纯培养肉汤的大肠杆菌O157:H7生长模型已被用于估计其在碎牛肉中的行为，尽管这些模型尚未在这种食品中得到充分验证。这种情况限制了对O157:H7大肠杆菌在碎牛肉中的行为的准确估计，并给风险评估带来了不确定性。在本研究中，我们测量了在10摄氏度下储存长达12天的零售碎牛肉中O157:H7大肠杆菌的单个和多个菌株的生长情况，并将结果与美国农业部病原体建模计划（PMP; version 5.1）的估计结果进行了比较。在pH为5.9时，PMP预测最大种群密度（MPD）为9.13 log10 CFU/g，指数增长率（EGR）为0.052 log10 CFU/h，滞后时间为56.3 h。然而，没有观察到滞后期。相比之下，零售碎牛肉的平均MPD和EGR分别为5.09 log10 CFU/g和0.019 log10 CFU/h，没有观察到滞后期。EGR和MPD均随脂肪水平的降低而升高。9株O157:H7大肠杆菌碎牛肉分离株的MPD和EGR参数变化不大。将两株本地竞争菌群分别添加到灭菌后的碎牛肉中，EGR和MPD随竞争菌群与大肠杆菌O157:H7的比例增加而降低。在1∶1、10∶1和100∶1的比例下，菌株的egr分别为0.033、0.025和0.018 log10 CFU/h， mpd分别为6.14、5.08和4.84 log10 CFU/g。这些结果表明，现有的基于肉汤的大肠杆菌O157:H7模型必须用于食品验证，模型应考虑食品基质、竞争菌群和潜在病原体菌株变化的影响。
Pure-culture broth-based models of the growth of Escherichia coli O157:H7 have been used to estimate its behavior in ground beef, even though these models have not been adequately validated for this food product. This situation limits accurate estimates of the behavior of E. coli O157:H7 in ground beef and introduces uncertainties in risk assessments. In the present study, the growth of single and multiple strains of E. coli O157:H7 were measured in retail ground beef stored at 10 degrees C for up to 12 days, and the results were compared with estimates generated by the U.S. Department of Agriculture's Pathogen Modeling Program (PMP; version 5.1). At pH 5.9, the PMP predicted a maximum population density (MPD) of 9.13 log10 CFU/g, an exponential growth rate (EGR) of 0.052 log10 CFU/h, and a lag time of 56.3 h. Similar parameter values were observed for sterilized ground beef; however, no lag phase was observed. In contrast, the mean MPD and EGR for retail ground beef were 5.09 log10 CFU/g and 0.019 log10 CFU/h, respectively, and no lag phase was observed. Both the EGR and the MPD increased with decreasing fat levels. There was low variation in the MPD and EGR parameters for the nine E. coli O157:H7 ground beef isolates. Two isolates of competitive native flora were separately added to sterilized ground beef, and the EGR and MPD decreased as the ratio of competitive flora to E. coli O157:H7 increased. For one strain, at ratios of 1:1, 10:1, and 100:1, the EGRs were 0.033, 0.025, and 0.018 log10 CFU/h, respectively, and the MPDs were 6.14, 5.08, and 4.84 log10 CFU/g, respectively. These results demonstrate that existing broth-based models for E coli O157:H7 must be validated for food and that models should consider the effects of the food matrix, the competitive microflora, and potential pathogen strain variation.