Monday, 6 June 2011

To Sprout or Not to Sprout

It's hard to think of anything more natural than organic bean sprouts, but for the last two days sprouts produced at an organic farm about forty miles south of Hamburg were held up as the likely source of a new and aggressive strain of e-coli that has killed 22 people,  and sickened more than two thousand more.  Late today (Monday) officials started backing away from this conclusion as new testing failed to find the e-coli on the farm's produce.  The owner of the organic farm says there is no manure used in the production of the sprouts, so doubts the farm could be the source, and it now looks like he could be right.  Even so researchers say  the supplier of the bean seeds sold to the farm needs to checked as well.

Deadly e-coli outbreaks, like the one in Walkerton, Ontario  are almost always linked to raw manure from cattle. Cattle have complex digestive systems full of various types of bacteria needed to breakdown the high cellulose diet they consume (grass and stored hay). The bacteria don't affect the cattle or the milk and meat produced, but if raw manure is mis-handled, and gets into drinking water, or onto produce, it can be a serious health risk.

Sprouts have always been a favourite target of public health officials during outbreaks because of the way they're produced commercially.  Many  use "steam barrels"  creating a warm (38 degree Celsius), moist environment that's good for germinating sprout seeds, but also a perfect environment for bacteria to grow quickly. The issue then becomes (like the current German situation) were the seeds used for sprouting clean or contaminated? Researchers are now saying the supplier of the bean seed is as likely a source as the farm itself..

It's now common for even organic producers of sprouts to bleach the seed before forcing it to germinate. The idea is that the bleach does not infiltrate the seed, but any bacteria or salmonella on the seed will be killed.

News reports out of Germany say the farm in question had delivered sprouts to virtually all the restaurants and stores linked to the outbreak, and given that sprouts have been a source of bacterial infections in the United States and elsewhere before, it seemed like a strong link.   Health officials had earlier blamed produce coming from Spain.  North Americans are just beginning to hear about the outbreak, even though the first cases were reported almost a month ago.

Here is a good backgrounder on e-coli.

E. coli, a friend that can turn lethal

June 02, 2011
Joseph Hall

Health Reporter

We are all full of E. coli. Wriggling microscopically by the billions in our bowels, multiple strains of the beneficial bacteria help us to digest food and to ward off illnesses.

But sometime around 1982, likely in the intestines of some western U.S. cattle, a version of the bacteria mutated.

It began to produce a poison – known as a shiga toxin -- that could be carried out of the animals in their manure, or saturate the meat they produced.

And for the first time, an E. coli organism, our constant companion though eons of evolution, was labeled as a health threat to humans.

Strains of that pathogenic version have since popped up in intermittent and usually isolated outbreaks around the world, like the one that killed some 18 people in Walkerton 11 years ago.

Now, another mutated E. coli strain is sickening people by the thousands in Germany.

But that E. coli germ, known as o104, is likely using the same mechanism to spread illness that all earlier pathogenic strains of the bacteria utilized, experts say.

“At some point, you had genes that produced toxins being shared between different organisms,” says Dr. Michael Gardam, head of infection control at Toronto’s University Health Network.

Gardam says the original pathogenic E. colis likely picked up a piece of DNA from a toxin producing bacteria known as shigella, a dysentery causing bug that killed off more troops than bullets did during World War 1.

And the new German version has surely done something similar, he says.

“It wouldn’t surprise me if you’ve got one producing a slightly different toxin,” Gardam says. “But I think the concept is exactly the same.”

These shiga-like toxins pose a double threat to humans.

First, they cause bloody and often explosive bouts of diarrhea. And for about 90 per cent of those infected, this unpleasantness will be the extent of it.

But for about 10 per cent, the toxin also attacks the blood’s red cells and platelets, and can lead to lethal conditions like kidney failure, Gardam says.

For these patients, he says, the body’s small blood vessels become inflamed, causing the red, oxygen carrying cells to “blow up” and the cut stemming platelets to run dry.

Shards of these wrecked cells can clog the blood cleansing kidneys, leading to renal failure, Gardam says.

But as in Walkerton, where a manure borne E. coli o157 strain made its way into improperly chlorinated town wells, the German outbreak is likely to be an isolated one.

Unlike viral pandemic pathogens, E. coli bacteria does not hitch rides within incubating airline passengers and jet it’s way around the world, says Tim Sly, a Ryerson University epidemiologist.

“You can be sitting next to someone with this particular disease in the subway, in the office…and you’re not going to get it from them,” Sly says.

The only way the disease can be transmitted, Sly says, is through ingestion, either of undercooked contaminated meat or actual fecal matter, usually lurking on the produce it helped fertilize.

Person to person transmission far more rare and often involves children who do not properly wash after using the washroom, says Marc Ouellette, head of infection and immunity with the Canadian Institutes of Health Research.

Sly does say, however, that a growing world trade in organic vegetables, which are grown exclusively with manure fertilizers, makes the chance that outbreaks could hit multiple regions from a common source more likely.

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