5种致泻性大肠埃希氏菌在生菜和圣女果上的生长特性研究

Study on the growth characteristics of 5 strains of diarrheagenic Escherichia coli on lettuces and cherry tomatoes

中文关键词:  致泻性大肠埃希氏菌  生菜  圣女果  温度  生长特性

英文关键词:diarrheogenic Escherichia coli  lettuce  cherry tomato  temperature  growth characteristic

中文摘要:

      目的 探究不同温度下5种致泻性大肠埃希氏菌在生菜和圣女果表面的生长特性, 为生食蔬果致泻性大肠埃希氏菌的风险控制提供理论基础。方法 在不同温度条件下(4、15、25和35℃), 在生菜和圣女果表面定量接种5种致泻性大肠埃希氏菌, 并定时检测样品中的细菌数量; 使用Origin 8.5软件拟合生长曲线, 建立修正的SGompertz模型和二次多项式模型, 对生长情况进行分析。结果 修正的SGompertz模型的相关系数R2大于0.98, 残差平方和小于0.15476; 二次多项式模型评价因子R2大于0.91, 偏差因子(bias factor, Bf)在0.90414~1.13815之间, 准确因子(accuracy factor, Af)在1.13745~1.84569之间, 说明模型拟合效果良好。不同菌株在同种基质上的生长规律基本一致, 表现为稳定期菌落数和最大生长速率随温度降低而减少, 达到相对最大生长速率所需的时间随温度降低而延长; 不同基质上的生长规律存在差异, 致泻性大肠埃希氏菌在圣女果上的生长速率极快, 最短时间(3~4 h)即可到达稳定期; 而在生菜上生长更为旺盛, 稳定期菌落数最高可达106 CFU/g。结论 修正的SGompertz模型可用于预测致泻性大肠埃希氏菌在生菜和圣女果上的生长情况, 低温冷藏可有效抑制致泻大肠埃希氏菌在生菜和圣女果中的生长, 为进一步降低风险, 建议在清洗之后, 立即将生食蔬果冷藏储存, 并尽快食用。

英文摘要:

      Objective To explore the growth characteristics of 5 strains of diarrheagenic Escherichia coli on the surface of lettuces and cherry tomatoes at different temperatures to provide theoretical basis for risk assessment and key control measures of diarrhegenic Escherichia coli on lettuces and cherry tomatoes. Methods Five strains of diarrheagenic Escherichia coli species were quantitatively inoculated on the surfaces of lettuces and cherry tomatoes, and cultivated at different temperatures (4, 15, 25 and 35℃), then the numbers of bacteria in the samples were regularly detected. The growth curves were fitted using Origin 8.5, the modified SGompertz models and quadratic polynomial models were established to analyze the growth situation. Results The correlation coefficients R2 and residual sum of squares of the modified SGompertz model were respectively more than 0.98 and less than 0.15476. The evaluation factors R2, bias factor (Bf), accuracy factor (Af) of the quadratic polynomial model were more than 0.91, between 0.90414 and 1.13815, between 1.13745 and 1.84569, respectively. It shows that the models fit well. The growth patterns of different kinds of diarrheagenic Escherichia coli were basically consensus on the same food substrate, showing that the stable period of colonies and the maximum specific growth rate decreased with the decrease of temperature, and the time required to reach the relative maximum growth rate increased with decreasing temperature. But the growth patterns existed differences when the food substrates were different. The growth rates of diarrheagenic Escherichia coli on cherry tomatoes were very fast, the shortest 3-4 hours to reach a stable period; while the growth was more vigorous on lettuces, and the total number of colonies in the stable period could reach about 106 CFU/g. Conclusion The modified SGompertz model can be used to predict the growth of diarrhegenic Escherichia coli on lettuces and cherry tomatoes. Cold refrigeration can effectively inhibit the growth of diarrhegenic Escherichia coli on lettuces and cherry tomatoes, it is recommended to refrigerate raw fruits and vegetables immediately after washing and eat them as soon as possible