短短两个月内，李斯特菌污染在美国已经导致16起不同的食品安全召回事件发生。为什么李斯特菌会出现在与细菌没有直接关联的产品中呢?一名美国堪萨斯州立大学的食品安全专家Fadi Aramouni给出了解释。

　　“李斯特菌是一类在湿冷条件下发现的细菌”，这位来自美国堪萨斯州立大学的食品科学推广专家说，”它的不同之处在于这种类型的细菌能够在冷藏条件下生长并繁殖“。

　　李斯特菌通常在即食的熟肉制品和热狗、冷藏肉制品、未经高温消毒的牛奶和乳制品、用未经高温消毒的牛奶制成的软奶酪、冷冻的烟熏海产品以及生豆芽中存在。

　　根据美国食品药品监督管理局的消息，自今年3月以来，16种可能含有李斯特菌的食品已被召回，包括鹰嘴豆、冷冻菠菜、沙冰等，最值得注意的是冰淇淋。

　　“冰激凌行业已经很长一段时间没有因为李斯特菌污染而发生过食品安全问题了，主要原因是由于其高温过程能够杀死存在的病原体，” Aramouni说， “然而，如果生产现场没有遵循严格的卫生操作规程， 那么李斯特菌可能也会存在于生产环境中，因为它能够在湿冷的条件下存活， 比如在管道中或者天花板、灯架上的冷凝水滴中，都可能发现它的存在。”

　　他还指出，冰激凌中的李斯特菌也可能来自于添加的食品配料中。

　　““对于冰淇淋的生产，人们可能不知道，会有一部分原料被加入以后，不再经过高温消毒过程了，”他说，“工人将牛奶高温消毒并制成冰淇淋以后，他们还会添加像饼干面团或山核桃之类的东西。但这之后，冰淇淋就被放置在冰箱中，也不再经过任何其他类型的杀菌消毒措施，所以，如果附加的原材料被污染，李斯特菌就会在这个过程中存活下来。”

　　不幸的是，现在没有办法能够让消费者知道是否某种食品中是否受到李斯特菌的污染。但是， Aramouni说也不必过于担心 ，只要关注食品安全召回信息，将列入召回目录的产品做退货处理或者直接扔掉就可以了，毕竟消费这样的食品是非常危险的。

　　谈到李斯特菌的危害性，Aramouni教授指出：“这种细菌能够导致死亡，特别是对于老年人、孕妇、儿童和免疫力低下的人群来说。他们感染了李斯特菌后，会有大约75%的人住进医院，而死亡率能够达到25%，这个比例是非常高的。所以不要冒险，如果发生食品召回事件，要积极应对 ，不要食用那些召回的产品。”

　　编译： 食安中国网

　　原文如下：

　　Listeria contamination has caused 16 different recalls in just two months, and a Kansas State University food safety specialist has an explanation about why it is appearing in products typically not associated with the bacteria.

　　“Listeria is a group of bacteria that is found in cold, wet environments,” said Fadi Aramouni, Ph.D., Extension specialist and professor of food science. “What’s unusual about this type of bacterium is they actually grow and multiply under refrigerated conditions.”

　　Listeria is typically found in ready-to-eat deli meats and hot dogs, refrigerated meat spreads, unpasteurized milk and dairy products, soft cheese made with unpasteurized milk, refrigerated smoked seafood, and raw sprouts.

　　According to the Food and Drug Administration, 16 different food products potentially containing Listeria have been recalled since March, including products such as hummus, frozen spinach, smoothie kits and, most notably, ice cream.

　　“A Listeria contamination in ice cream hasn’t happened for a very long time because the pasteurization process kills the pathogen,” Aramouni said. “However, Listeria may survive in the environment if there are not good sanitation procedures in place. Because it survives in cold, wet environments, it can be found in drains or other areas of condensation within a plant, such as the ceiling or light fixtures.”

　　He says the Listeria in ice cream also could be coming from the added ingredients.

　　“One of the things people may not know about ice cream is that it is not pasteurized after the inclusions are put in,” he said. “After they pasteurize the milk and make the ice cream, they add things like cookie dough or pecans. The ice cream is then placed in the freezer and does not go through any other type of pasteurization, so if the additional products are contaminated, Listeriamay survive that process.”

　　Unfortunately, there is no way for consumers to tell if a product is contaminated with Listeria. But Aramouni said not to panic. Instead, pay close attention to food recalls and return the product or throw it out if it has been recalled because consuming the product can be dangerous.

　　“This bacterium can be deadly, especially for older adults, pregnant women, young children and people with weakened immune systems,” he explained. “About 75 percent of these individuals who get listeriosis end up in the hospital, and about 25 percent of them die, so it is quite virulent for this group. Don’t take chances. Anytime there’s a recall, respect that recall and do not consume the food.”