Food safety investigation of E. coli O121 in flour products

The Canadian Food Inspection Agency (CFIA) is committed to the continued improvement of Canada's food safety system. The CFIA is also dedicated to reporting on food safety incidents that have caused serious illnesses in Canada or otherwise have significant interest to the Canadian public.

This report provides a summary of the CFIA food safety investigation and recall activities in response to the 2017 outbreak of E. coli O121 illnesses linked to the consumption of flour, and outlines lessons learned and the CFIA's follow-up actions.

Background

On January 4, 2017, the CFIA was notified by the Public Health Agency of Canada (PHAC) of an outbreak of E. coli O121 human illnesses under investigation by a number of provincial health authorities. An Outbreak Investigation Coordination Committee (OICC) involving PHAC, the CFIA, Health Canada and all implicated provincial health authorities was activated.

Initially, no specific food source could be identified as the cause of the outbreak. Early indications pointed to a number of possibilities as the source of the illnesses. As new cases were reported and the epidemiological investigation progressed, investigators identified a possible link with uncooked flour, with several cases reporting contact with Robin Hood flour. The testing of a remaining portion of flour at a case's home and of intact flour products sampled at retail led to the first recall of flour on March 28, 2017. Further product sampling and testing, whole genome sequencing analysis, and the identification of processing linkages at the flour mill led to several additional recalls of flour products between April and June 2017, expanding to other flour brands and a number of raw bakery products.

On June 2, 2017, PHAC closed the national outbreak investigation and declared the outbreak over as no new cases had been reported since April 2017.

A separate outbreak from a different strain of E. coli O121 in British Columbia was also reported during the same period. Analysis of an open bag of flour from a case's home and of intact bags of the same flour confirmed the presence of E. coli O121 in one lot code of Rogers brand all-purpose flour. This lot code was subsequently recalled on June 7, 2017.

CFIA activities

From the onset of the national outbreak investigation, the CFIA pursued a number of lines of enquiry of possible food sources of the illnesses. During the outbreak investigation, one of the affected individuals who reported having been in contact with Robin Hood flour still had the product available at home. This sample was analysed by Alberta Health Services and was reported as E. coli O121 positive on March 22, 2017. The CFIA located and tested two intact bags from the same production lot of flour and confirmed the presence of E. coli O121 in one code of Robin Hood brand All Purpose Flour, Original, which had been produced on October 17, 2016.

This finding led to the first flour recall, on March 28, 2017, by Smucker Foods of Canada Corporation who proceeded with a voluntary recall of the implicated lot code. The CFIA issued a Food Recall Warning on March 28, 2017, identifying distribution in British Columbia, Alberta, Saskatchewan and Manitoba, and issued an updated warning on April 4, 2017 to inform consumers of the product's national distribution.

Following the March 28, 2017 recall, the CFIA applied a systematic approach to determining whether any other flour lot codes could be affected. This involved sampling and testing of a broad range of flour products manufactured by Ardent Mills, Saskatoon, the mill where the implicated flour originated. Sampling covered flour production ranging from September 1 to November 30, 2016.

The sampling activities initially generated two positive findings of E. coli O121 in Robin Hood brand All Purpose flour produced on October 15 and 16, 2016. Based on this information, on April 12, 2017, Ardent Mills proceeded with a voluntary recall of a wide range of flour products manufactured between October 14 and 18, 2016 and sold under various brand names. The scope of recalled products was established by examining commonalities of source material and process flows and on the basis that flour produced within the identified timeframe could not be effectively differentiated from the flour that led to positive laboratory findings. The CFIA updated the Food Recall Warning on April 12, 2017.

Another positive result for E. coli O121 was subsequently reported in Robin Hood brand blending flour produced on November 3, 2016. Based on the new laboratory result and verification of source material and process flows, Ardent Mills proceeded with a voluntary recall of various brands and varieties of flour products packaged on November 2 and 3, 2016. The CFIA issued a Food Recall Warning on April 16, 2017 in respect of recalled product sold at retail.

Ardent Mills with support from the CFIA undertook extensive trace back activities by reviewing raw grain input, production records and processing information to identify possible common inputs to the affected flour. Based on the review, on May 26, 2017, Ardent Mills proceeded with a voluntary recall of a broader range of flour products milled from October 4 to November 14, 2016. An updated Food Recall Warning was issued to communicate information regarding products distributed at retail.

The CFIA also followed-up with food companies that had received recalled flour. This resulted in a number of recalls of raw flour based products by distributors, bakeries and retailers, and a number of associated Food Recall Warnings issued by the CFIA. The recalled products were considered a risk to consumers on the basis that they were made from recalled flour and offered for sale in a raw state (e.g. raw dough, uncooked pie crust, etc.).

During the same period, a separate outbreak of E. coli O121 illnesses was reported in British Columbia. The strain of E. coli was different from the concurrent national outbreak. The British Columbia Centre for Disease Control issued a Public Advisory on May 19, 2017 advising consumers not to eat a certain lot code of Rogers brand all-purpose flour, based on a positive finding of E. coli O121 in an open bag of flour sampled at a case's home. Follow up sampling and testing of intact bags conducted by the CFIA confirmed the presence of E. coli O121. On June 7, 2017, Rogers Foods Ltd. voluntarily recalled the affected product and the CFIA issued a Food Recall Warning.

Conclusions

The CFIA, Ardent Mills and Rogers Foods Ltd. were unable to specifically identify the source of the E. coli O121 contamination in the respective flour products. The wheat from which the affected flour was manufactured is a raw agricultural product that is exposed to possible sources of contamination during growing and harvesting. Most flour in North America is manufactured without the application of a step to kill pathogenic bacteria.

The presence of pathogenic E. coli in flour has only been recognized recently as a concern. It is mainly after the 2015-2016 multi-state outbreak of E. coli illnesses in the USA and this recent outbreak in Canada that flour has gained attention as a potential vector for pathogenic E. coli.

It is highly possible that the presence of pathogenic E. coli in flour was under reported and that the introduction of advanced methods to detect pathogens together with new analytical approaches used by PHAC and the CFIA in outbreak investigations have increased our ability to identify causes of illnesses, including new food-hazard combinations such as E. coli in raw flour.

Lessons learned

  • The grain distribution chain is very complex. Flour may be produced from blending several domestic and imported types of wheat grains to obtain the desired characteristics. This outbreak highlighted the challenges of identifying the source of contamination, and underscores the importance of encouraging millers and other processors and distributors to maintain strong traceability systems all along the production and distribution chain.
  • It is CFIA's practice to engage affected national industry associations during complex or broad impact food safety investigations. This investigation was particularly challenging as it revealed a food safety concern in an unusual food commodity. The event highlighted the importance of broadening and enhancing CFIA communications in general, and more specifically for situations that involve national industry associations not normally affected by foodborne illness outbreaks.

Actions taken by the CFIA and the industry

  • The CFIA has been actively engaged in an Industry/Government Ad Hoc Advisory Committee to identify research needs relating to E. coli in cereal grain-based foods, and with the Canadian Grain Commission to assist with research on the occurrence and frequency of human pathogenic bacteria in wheat and other grain cereals. The CFIA is also collaborating with multiple provincial, federal, and international partners to explore testing protocols and alternative detection methodologies.
  • The Canadian industry has also been actively working on this issue. In addition to leading the Ad Hoc Advisory Committee and participating in several research projects, some industry members have begun the voluntarily labelling of retail bags of flour with messages such as "Do not eat raw flour, dough or batter" to better inform consumers.
  • The CFIA reached out to the US government and other international partners via the International Food Safety Authorities Network (INFOSAN) to ask about their experience and approach. It appears that most of the international community has not implemented specific actions to mitigate the risk of pathogenic E. coli in flour.
  • Once we have a better understanding of the incidence, potential sources, industry practices and environmental factors that may have contributed to the outbreak, the CFIA will engage with federal and provincial partners to consider more risk mitigation actions along the supply chain.

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