Q&A: A Food Safety Expert Explains Germany's E. Coli Outbreak

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Farmer Tim Voges destroys lettuce in Ronneburg, Germany, on May 27, 2011, after fears of a deadly E. coli contamination spread throughout the country



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Obviously there are vast differences between E. coli — some that cause no diseases and then types that cause severe infections. Some serotypes cause urinary tract infection, some cause diarrhea, but most don't cause the severe type of thing we're seeing right now. The outbreak in Germany is caused by one of the serotypes that is very severe.


What do we know about this type of E. coli?

There are six serotypes known as the 'Big 6' that are commonly associated with severe types of diseases like kidney failure, severe diarrhea. [The serotype in Germany] is a new one and it's intriguing: one key gene we thought was important for E. coli to cause severe illness was one that encodes intimin, which allows E. coli to intimately attach to human intestinal cells. This serotype doesn't have that gene, which is really surprising. So there's something unusual going on; a lot of the evidence suggests it's a very unusual bacterium.

If this type of E. coli doesn't have the key genetic capability, how is it making people sick?

One of the other genes that's important is carried by a virus, which can move genetic material from one bacteria to another. Phages, viruses that can infect bacteria, often introduce new genetic material, so you might see an emergence of some traits that way. They can move genetic material from one bacteria to another — including going between serotypes. One of the genes that's important [that causes illness] is a gene that can carry toxins from one E. coli to another E. coli.

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But even though some E. coli have intimin and some don't, what seems to be the key factor is the combination of having intimin and making shiga toxins. The toxin gets into the bloodstream, causing illnesses like severe diarrhea and even kidney failure.

What's the treatment for people with this toxin?

It's difficult to treat. Traditionally, you'd treat it with antibiotics, which kill bacteria. But in this instance, the E. coli makes a toxin which is found in the cell, so what happens if you kill the cell? The toxin is released into the blood stream and what happens then? The infected person gets even sicker. So really you shouldn't treat these people with antibiotics. They are trying a new therapy right now in Germany that neutralizes the toxin.

Is E. coli most often found on vegetables?

No, E. coli isn't found there more often. It's simply that the problem with fresh produce is you don't cook it. Cucumbers you won't cook. That's what makes the presence of these organisms on fruits and vegetables more challenging. Those types of foods cause illness more often, but I wouldn't say E. coli is found there more often.

Where does it come from?


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So do most cases of infection come from contact with ruminants?

Human infections are often traced back to ruminant-associated sources — undercooked ground beef — but also things like apple cider that have nothing to do with cows. In these cases, maybe the apples were contaminated with deer fecal matter. Of course it's a circular argument: because we all believe that O157:H7 will always come from ruminant digestive tracts, whenever there's an outbreak we're all looking for evidence of that. And if you look hard enough for something, you're going to find it. But we're not always 100% sure.

If the European outbreak didn't originate in cucumbers from Spain, as German officials thought, what else could be the source of contamination?



But it could also be through humans. Someone handles produce and doesn't follow proper procedure for hand washing.


The problem with all this is that it really is everyone's responsibility and everyone contributes their part to it. Beyond the specific outbreak, [it's important to] have practices on fields to minimize the presence of animals and to have proper procedure in processing, including testing the environment to see whether E. coli is present.

Also, basic things that you've always been taught: don't use the same cutting board for chicken and salad. Wash your produce. Cook things through. A major source of E. coli poisoning is still undercooked ground beef. Don't make it medium rare or rare. There needs to be a responsibility to everyone along the whole chain.

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