Evolution Creates Dangerous E. coli Strain
The E. coli strain that has sickened thousands in Germany is a combination of two E. coli strains, according to research published in the journal Lancet Infectious Diseases:
- Enteroaggregative E. coli (EAEC)—which stick to the intestinal lining with a “stacked brick” adherence pattern and usually cause prolonged, watery diarrhea.
- Shiga toxin-producing E. coli, or STEC—which causes hemorrhagic colitis (bloody diarrhea and can result in hemolytic uremic syndrome (HUS), a leading cause of kidney failure.
This deadly combination was the result of evolution. "The most likely scenario is that an EAEC strain acquired the ability to produce Shiga toxin from a STEC strain," Edward Dudley, an assistant professor of food science at Penn State told Penn State Live.
E. coli can swap genetic material across different E. coli strains and across bacterial species, according to Dudley:
It's a fascinating organism because it has the ability to pick up new genes from other organisms and evolve into a variety of types. It's like they're playing a game of poker and shuffling cards back and forth and somebody comes up with a jackpot hand that allows it to become something nasty.
Dr. Helge Karch of the University of Münster and team leader of the research published this week told the New York Times:
“I think it is human-specific,” Dr. Karch said. And that increases the mystery of where it goes between outbreaks.
Dr. Karch thinks it smoldered in human populations, causing mild illnesses in most and occasionally causing severe disease. Then, somehow, it was passed to the bean sprouts by someone who harbored the bacteria. And since sprouts are eaten raw, they were highly infectious.
The strain is so rare, Dr. Karch said, that those infected had no immunity. An epidemic caught fire.
