Detection of Shiga Toxin-Producing Escherichia Coli in Flour

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To date, Australia has avoided Shiga toxin-producing Escherichia coli (STEC) detections and outbreaks in flour, but that does not mean we are exempt. We need to take as much information as we can from any incident, whether overseas food safety incidents or at home.

In May 2016, General Mills (USA) voluntarily recalled wheat flour in response to a number of reported illnesses from people who had eaten or handled raw dough. In June 2016, the US Food and Drug Administration (FDA) detected the presence of E. coli O121 in flour from General Mills. Further detection of E. coli O26 was also found to be present, prompting an expanded recall.1 2

The FDA found that flour produced in the period November 2015 to February 2016 from the General Mills facility in Missouri was the original source.1 No confirmed information is available as to how the flour was contaminated. E. coli normally lives in the intestines of humans and animals so contamination could have occurred as far back as the farms on which the wheat was grown.

To date, at least 63 people have taken ill including 17 hospitalisations and one (1) with a life-threatening kidney condition caused by the Shiga toxin.1 The long shelf life of flour complicates the situation as products may still be in consumer’s pantry, therefore further cases of illness may still occur.

The General Mills supply chain was also affected. Clear Springs Foods Inc. detected E. coli in the flour purchased from its supplier who sourced it from General Mills.2

What are STEC?

Most strains of E. coli are harmless and sometimes even beneficial. Some however produce Shiga toxins, referred to as pathogenic E. coli. Shiga toxins are potent bacterial toxins produced by Shigella dysenteriae and some pathogenic E. coli which can cause serious illness in people. E. coli O157, O26, O103, O104 and O121 are examples of Shiga toxin producing E. coli.

Considerations for Australian food processors

While Australia does not have the number and variety of incidents and recalls that are reported overseas, our food safety systems still need to be robust. Based on the outbreak information, dry goods such as flour should be considered in STEC risk assessments. As such, food processors should consider the following.

  • Do you need to review the microbiological hazard potential in the dry ingredients you use as a result of this information? While low moisture foods do not support the growth of pathogens they can still survive and cause illness when incorporated in higher moisture products.
  • Do you use raw flour in your products? Would using heat treated flour be an option?
  • Is there a need to attach a warning label saying not to eat your product raw? Is this covered in your storage/cooking instructions?
  • Is there a chance your product that is meant to be eaten cooked could be consumed raw? Do you factor this in to your Product Description and Intended Use for HACCP?

For further information about how Symbio Laboratories can assist you with your testing requirements, simply call 1300 703 166 or email


1 US Food and Drug Administration, FDA Investigated Multistate Outbreak of Shiga toxin-producing E. coli Infections Linked to Flour, 29 September 2016 (accessed 18 October 2016).

C. Heneghan, Food Dive, General Mills recall expands again — this time, to trout,, 12 October 2016 (accessed 18 October 2016).

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