Non-thermal methods to disinfect enterohemorhagic Escherichia coli contamination in salad vegetables

用含绿色荧光蛋白基因的质粒转染肠出血性大肠杆菌O157。人工污染生菜是通过将叶子浸泡在细菌悬浮液中来生产的。忽略已有菌群，准确计数O157在紫外照射下的荧光。在本研究中，考察了各种化学试剂和处理条件的消毒效果。加热壳粉溶液对生菜的杀菌作用强于次氯酸盐。部分接种菌似乎侵入了生菜组织内部，在药物难以到达的地方完美地杀死了它。经壳粉溶液浸泡后低温保存8 ~ 24小时，可杀灭O157病菌。生物保存正在成为食品安全的重要手段。虽然从人类粪便标本中分离到对O157有抑制作用的细菌，但在整个实验过程中，没有在正常的食物菌群中发现这种细菌。初步试验表明，脉冲功率放电有可能降低生菜上O157的污染水平。

A strain of enterohemorrhagic Escherichia coil O157 was transformed by the plasmid which contained the green fluorescence protein gene. Artificially contaminated lettuce was produced by soaking the leaves in the suspension of the bacterium. Neglecting preexisting bacterial flora the number of O157 were accurately counted for their fluorescence under irradiation of UV. Throughout this research various kinds of chemical reagents and treatment-conditions were examined for disinfecting effects. Heated shell-powder solution showed strong bactericidal activity on lettuce rather than hypochlorite. A part of the inoculum seemed to have invaded to lettuce organization inside where the drug is difficult to reach and perfectly kills it. The O157 organisms were killed in 8-24 hour, when the lettuce was preserved at the low temperature after soaking in the shell-powder solution. Biopreservation is becoming attractive method for food safety. Although bacteria showing inhibitory effects against O157 were isolated from the human fecal specimens, it was not found among normal bacterial flora of foods throughout the experiments. It was suggested through some preliminary experiments that pulsed power electric discharge could possibly reduce the level of O157 contamination on lettuce.