E.coli O157 & Haemolytic Uraemic Syndrome

A novel antimicrobial peptide significantly enhances acid-induced killing of Shiga toxin-producing E.coli strains

19th July 2011

A new study published in July's edition of Microbiology focuses on a novel peptide - a protein too small to merit the title. Known as wrwycr, it has proven to disrupt E. coli bacteria's natural ability to repair its DNA after damage from stomach acid.

Early lab tests show that after contact with this peptide, Shiga toxin-producing strains of E.coli die off in stomach acid faster than is necessary to enter human intestines, where they cause the medical complications associated with the toxin. Non-Shiga toxin producing E.coli suffer similar fates, but pose little concern in comparison.

Though the team is far from achieving its ultimate goals, the big idea is to use this peptide in a spray or wash for fruits and vegetables, essentially weakening potential pathogens before anyone even chomps into the produce. So far, they've only completed the initial tests to prove the theory might work.

"We exposed pathogenic E. coli to this peptide for five minutes at room temperature -- and of course compared them to bacteria that had not seen the peptide. The results were profound," said Debora Foster, Ph.D., cellular biology professor at Ryerson University and the study's lead author. "We were seeing dramatic differences in the survival rates after acid treatment."

Along with Dr Anca Segall from San Diego State University and Dr Steve Goodman from the University of Southern California, Foster's team tested the survivability of several E.coli strains - including the well-known O157:H7 - in acid with and without the peptide.

Without it, large, viable numbers of bacteria still survived in the acid after many hours -- long enough to move on to colonize the intestines. A meal will typically pass through the stomach over 4 to 5 hours. But after exposing O157:H7 bacteria to the peptide, the team couldn't detect any E.coli after as little as 30 minutes in the acid.

The survival rates of other strains varied, but each dropped significantly when exposed to the peptide. The team members have not been able to test E.coli O104:H4, the strain behind the European outbreak, but they hope to receive a sample soon.

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