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Why bean sprouts are at risk of the E coli outbreak

Roz Zurko's picture

Bean sprouts are grown in a way that renders them at risk for containing the E coli bacteria inside their tubes, where washing won't rid the E coli bacteria.

The E coli outbreak was first thought to be caused by Spanish cucumbers, then salad vegetables, now it is bean sprouts that are the prime suspects in the search for a source of the European E. coli outbreak. While the other suspected sources proved wrong, it looks as if the health authorities in Germany have found the original source this time.

German officials believe they have found a connection with the E coli infected patients and bean sprouts grown at one farm in Uelzen, south of Hamburg. The officials are waiting for further test results to confirm their suspected link, but there seems the most probable of causes so far, according to the BBC.

Bean sprouts have been the source of a health scare before, including adzuki, alfalfa, lentils and mung beans. In 2010, bean sprouts were linked to an outbreak of Salmonella and since 1996, beans sprouts have been linked to 30 outbreaks in the US. Why bean sprouts? The way that they are farmed and the preparation techniques used in kitchens at home offer potential risks. Bean sprouts can contain the E coli bacteria inside the sprouts, so even washing the sprouts would not remove the E coli from this vegetable. Dr. Stephen Smith, a clinical microbiologist at Trinity College Dublin explains that if seeds contain the E coli bacteria, the bean sprouts can grow containing this bacteria inside the sprout.

Salads are often served with bean sprouts and if the vegetable is contaminated then eating it raw could be a health risk. Sprouts should be cooked thoroughly until they are steaming hot, according to the Food Standards Agency. It also advises to rinse the sprouts thoroughly before cooking and not eating them after the use by date.

Farm bean sprouts are grown from seeds in steam drums at a temperature of 38C, according to the BBC.

E coli outbreaks come from many sources, this is why it is hard to trace back the steps when an outbreak occurs. E coli outbreaks can come from the water used to irrigate the vegetables or they way the vegetables have been handled or from the many steps in between. It is just hard to say where it all stems from. After weeks of investigation it does look as if the authorities in Germany might have the original source this time. Here are some of the other things associated with past E.coli outbreaks,

* Processed meats: hamburgers, kebabs and salami
* Cheese, milk, butter, yoghurt, ice cream and other dairy products
* Salad vegetables such as coleslaw, lettuce, spinach, radishes and alfafa sprouts
* Fruits including melons, grapes and apple juice
* Waterborne outbreaks associated with lakes, ponds, paddling and swimming pools

The Agriculture Minister for Lower Saxony, Gert Lindemann, says about the farm they have targeted as the origin of this newest E coli outbreak, "this is "ideal" breeding ground for all bacteria."

The bacterium normally lives in the stomach of animals and E. coli outbreaks can start when feces are used as fertilizer or when the water is contaminated by feces. The authorities are uncertain how the O104 strain of E. coli would get to this farm in the first place. This is still an on going investigation which will hopefully yield all the unanswered questions. The farm has been shut-down by authorities. By finding the source and how the E coli got to the source in the first place, this could help guard against outbreaks in the future.

Klaus Verbeck, who is managing director of the farm in Germany, which is the farm believed to have grown the tainted bean sprouts, is saying that their procedures for growing the bean sprouts do not offer these risks. "The salad sprouts are grown only from seeds and water, and they aren't fertilized at all. There aren't any animal fertilisers used in other areas on the farm either, " says Verbeck.

Even if the tests done on the bean sprouts at the farm confirm this is where the E coli outbreak originated from, this might not be the ultimate source, according to the BBC.

"E. coli can stick tightly to the surface of seeds needed to make sprouts and they can lay dormant on the seeds for months, during germination the population of bugs can expand 100,000 fold, according to Dr Stephen Smith, a clinical microbiologist at Trinity College Dublin.

Smith continued on to explain why in this case even washing this vegetable would not have been any help against transmission of E coli. "However, and this is probably the key to the German outbreak, the bacteria are inside the sprout tube as well as outside. Thus washing probably had no effect. The bottom line is that it is crucial to source where the seeds came from and recall any stock," reports Smith.

Reference: BBC, Food Standards Agency UK

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