Lettuce Outbreak

Soon after the Centers for Disease Control and Prevention called Tuesday for stores, consumers and restaurants to throw away their supply of romaine lettuce, several Madison restaurants reshuffled their menus.

Q: How do crops become carriers

of E. coli?

A: Dozens of cases of sickness from a toxin-producing strain of E. coli have been linked to romaine lettuce in recent weeks, according to the Centers for Disease Control and Prevention. UW-Madison professor Jeri Barak said there are several reasons lettuce or other crops can carry these bacteria.

Bacteria can get on crops through animals carrying bacteria entering the fields, contaminated water and improperly composted manures, Barak said.

“These are rare events,” Barak said. “However, many of the crops that have become problems lately are harvested and then dumped into a wash tank post-harvest, so a small number of bacteria from one plant could then be spread to lots of leaves in the wash.”

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Barak said bacteria could be in or on lettuce or other crops and it cannot be washed off. Cooking contaminated produce would kill the bacteria, Barak said.

Not all E. coli is bad for humans, Barak said, just the strains that make Shiga toxin. “Humans need to have E. coli in their gut to be healthy — just not the ones that produce these toxins.”

The CDC recommends consumers do not eat or buy products containing romaine lettuce unless they can confirm it was not grown in the Yuma region of Arizona, the source of the current outbreak.

— Shelley K. Mesch

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