Tuesday, August 5, 2008

E. coli O157:H7 - A Bedtime Story

Once upon a time, there was a microbe by the name of E. coli. One day, while our little friend – who preferred to be called "Big Eddie" – was browsing in an intestinal flea market, the devil (disguised as a merchant) whispered into his ear.

"Psst, Big Eddie," said the devil, "aren't you cold? Let me sell you this nifty model O:55 coat."

"Sure," said Big Eddie, "I'll take it. What's the price?"

"Don't worry," replied the devil, "you can pay me later."

Next time Big Eddie went for his flea market walk – wearing his new coat, of course – he passed by the devil's booth again.

"Psst, Big Eddie," said the devil, "wouldn't you rather swim? I have some lovely flagellae to offer. They're the latest model – H7 – and would suit you perfectly."

"Sure," said Big Eddie, "I'll take them. What do I owe you?"

"Don't worry," replied the devil, "you can pay me later."

Big Eddie continued through the market, swimming slowly as he got used to his new appendages. As he went, the devil followed and whispered into his ear again.

"Psst, Big Eddie," said the devil, "those model H7 flagellae look real cool on you. But they don't really go with your old O:55 coat. Why not upgrade to this brand-new model O157 that just came out?"

"Great idea," Big Eddie replied, "I'll take it."

And that's how Big Eddie acquired his new coat.

After a while, Big Eddie got tired of his intestinal home and decided to travel. So he swam towards the light and landed plunk in the middle of a field – surrounded by cattle. It was raining hard, and Big Eddie allowed himself to be carried by the runoff to a nearby stream.

After a while, he found himself a long way downstream from his old home, and began to feel lonely. Imagine how happy he was to encounter a familiar face. The devil had followed him.

"Psst, Big Eddie," said the devil, "how would you like to become so powerful that industrial giants and politicians will bow down to you? You'd be able to live anywhere in the world. You'll multiply and produce billions of descendants. You'll never be lonely again."

"Wow," replied Big Eddie, "that sounds wonderful! What do I have to do?"

"Not much," answered the devil "except that you and your offspring won't be able to digest sorbitol or produce glucuronidase enzyme."

"That's no big deal," Big Eddie answered immediately, "I never did like the taste of sorbitol anyway. And who needs glucuronidase?"

"OK," said the devil "I'll send my agents along with their power tools."

And before he knew what was happening to him, Big Eddie was attacked by a swarm of the devil's bacteriophages. They injected him with pieces of DNA stolen from an unsuspecting Shigella, which happened to be swimming nearby. The DNA contained a blueprint for producing two toxins.

A pathogen was born. And the devil had the last laugh.

~ The Beginning ~

OK. So it didn't happen exactly that way. The real story can be found in Chapter Six, "Birth of a Pathogen" of Food Safety: Old Habits, New Perspectives.

E. coli O157:H7 is thought to have evolved in several steps from an ancestral strain of E. coli. It first was linked to human illness in California in 1975, when it was isolated from the stool of a woman who was suffering from bloody diarrhea. In 1978, it was recovered from a patient in Ottawa, Canada. The rest, as they say, is history.


  1. Please pass me my blankie..

    Informative bedtime story, Cuzzie!

  2. Sweet dreams, Cuzzie. Here's the blankie.


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