Three strains of Escherichia coli 0157:H7 (ATCC 43895, Ent C9490 and 380-94) were inoculated into salami and heated in water baths at 50, 55 or 60 deg C. At intervals between I and 360 min, salami samples were removed from the water bath and examined for the presence of surviving E. coli 0157:H7. Samples were directly plated onto sorbitol MacConkey (SMAC) agar, and onto tryptone soya agar (TSA) with SMAC overlay. The number of sub-lethally damaged cells in each sample was estimated from the differences between the resultant direct (uninjured cells only) and overlay (total recovery) counts. In samples heated at 50 deg C, the percentage of cell injury ranged from 71.8-88 for all strains. In samples heated at 55 deg C the percentage of sub-lethally damaged cells in strains A TCC 43895 and Ent C9490 was significantly higher (P < 0.001) at 97 than that observed in strain 380-94 (64). Cell injury was not measured at 60 deg C. There were significant differences between the derived decimal reduction times (D-values) related to the different strains of E. coli 0157:H7, the heat treatment applied and the recovery/enumeration agars used. Significant interstrain differences (P < 0.05) in thermotolerance were noted. Strain Ent C9490 was significantly more heat resistant at 50 deg C and 60 deg C (D-values of 116.9 and 2.2 min, respectively), while at 55 deg C strain 380-94 was more thermotolerant (D-value of 21.9 min). The implications of these findings for the design of studies investigating the heat resistance of E. coli 0157:H7 in fermented meat environments are discussed.
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机译：将三种大肠杆菌 0157：H7（ATCC 43895、Ent C9490 和 380-94）接种到意大利腊肠中，并在 50、55 或 60 摄氏度的水浴中加热。在I和360分钟之间的间隔，从水浴中取出萨拉米香肠样品，并检查是否存在存活的大肠杆菌0157：H7。将样品直接接种到山梨糖醇MacConkey（SMAC）琼脂和胰蛋白胨大豆琼脂（TSA）上，并覆盖SMAC。根据所得的直接（仅未受伤细胞）和叠加（总回收）计数之间的差异估计每个样品中亚致死性损伤细胞的数量。在50°C加热的样品中，所有菌株的细胞损伤百分比范围为71.8-88%。在55°C加热的样品中，菌株A、TCC 43895和Ent C9490中亚致死性损伤细胞的百分比显著高于菌株380-94（64%），为97%（P<0.001）。在 60 °C 下未测量细胞损伤。与大肠杆菌 0157：H7 的不同菌株、所应用的热处理和使用的回收/计数琼脂相关的衍生小数还原时间（D 值）之间存在显着差异。注意到耐热性存在显著的应变间差异（P<0.05）。菌株 Ent C9490 在 50 °C 和 60 °C 时具有显著更高的耐热性（D 值分别为 116.9 和 2.2 min），而在 55 °C 时，菌株 380-94 的耐热性更强（D 值为 21.9 min）。讨论了这些发现对研究大肠杆菌0157：H7在发酵肉环境中的耐热性设计的影响。
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