Genome sequencing links recalled flour to E. coli outbreak

June 16, 2016

E. coli bacteria

Several weeks after a massive flour recall due to E. coli contamination, health officials are reporting they have found the “smoking gun” in the investigation, matching E. coli O121 from a sample of flour recovered from a sick person’s home to the outbreak strain that has sickened at least 38 people since December.

The strain of E. coli was identified using whole genome sequencing (WGS), which has been integrated into routine foodborne disease surveillance over the past five years. Allowing scientists to match specific strains of foodborne pathogens in cases the span multiple states over extended periods of time, WGS has greatly improved the tracking and identification of foodborne illness outbreaks.

In this case, outbreak victims were spread across 20 states as of May 3, which was the most recent illness onset date reported by Centers for Disease Control (CDC). The first confirmed victim became ill Dec. 21, 2015.

Because the flour recall was so large, public health officials are concerned that consumers may still have the recalled flour in their homes.

Dr. Karen Neil, a medical epidemiologist with CDC’s Outbreak Response and Prevention Branch, said consumers should check packages they have on hand and throw the flour away if the label codes match those of the recalled products.

“Unfortunately flour is one of those things that people usually transfer to their own containers when they get home from the store, Neil said in an article. “If that’s the case and you don’t know if your flour is part of the recall, it’s best to follow the food safety rule, "When in doubt, throw it out."

“They should also be sure to thoroughly wash the container and their hands, as well as anything that came into contact with the flour.”

Neil said even if consumers plan to use the flour in baking or cooking that would provide a kill step, the flour can very easily cross-contaminate utensils, surfaces and other foods during preparation. She also repeated the CDC’s standing warning about raw dough.

“It is very important for people to never eat raw dough or batter,” Neil said, explaining that there is the inherent possibility for raw flour to be contaminated because it is made from wheat, which is grown outdoors, and not subjected to a kill step during production.

Anyone who has eaten or handled raw dough or batter and develops symptoms of E. coli infection should immediately see a doctor and be tested.

According to the CDC, people usually become ill from E. coli O121 within 2–8 days after consuming the bacteria. Most people will experience diarrhea, which is often bloody, and abdominal cramps. For most, recovery time is about one week.

Some E. coli illnesses last longer, however, and can be more severe, resulting in a type of kidney failure called hemolytic uremic syndrome (HUS). HUS can occur in people of any age, but is most common in young children under five years, older adults, and people with weakened immune systems.

Symptoms of HUS can include fever, abdominal pain, pale skin tone, fatigue and irritability, small, unexplained bruises or bleeding from the nose and mouth, and decreased urination.

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While WGS is powerful, early detection methods can provide insight for processors information on the type of E. coli. Neogen’s genomic testing service for Shiga toxin producing E. coli (including O121) is NeoSeek. NeoSeek provides confirmation results for STEC presumptive samples in 24 hours.


Category: Food Safety, Food & Beverage, Bacterial Sequencing