Consumption of raw flour can lead to E.coli, claims study

By Jenny Eagle

- Last updated on GMT

Study claims raw flour can lead to E.coli. Photo iStock/Mercava.
Study claims raw flour can lead to E.coli. Photo iStock/Mercava.

Related tags Escherichia coli

Consumption of raw flour can lead to E.coli, according to a study in The New England Journal of Medicine.

Its report, ‘Shiga Toxin–Producing E. coli​ (STEC) Infections Associated with Flour’, published this month​, claims in 2016, a team investigated an outbreak of STEC serogroup O121 and O26 infections linked to contaminated flour from a large domestic producer and implicated raw flour was the source.

Raw cookie dough

Between December 2015 and September 2016, there were 63 cases where flour was found to be responsible for causing food-borne illnesses in Canada and the US.

In two of the cases, the victims confirmed they had eaten raw cookie dough made from the same brand of flour.

A total of 24 states in the US alone reported cases, one of which resulted in a patient having haemolytic uremic syndrome, a form of kidney failure. 

By February 2016, the Centers for Disease Control and Prevention identified the uncommon strain​ causing the outbreak as serogroup O121.

The research led to more than 10 million pounds of flour being recalled.

Although it is a low-moisture food, raw flour can be a vehicle for foodborne pathogens​,” said Samuel J Crowe, lead author of the study and epidemiologist at the division of food-borne, water-borne and environmental diseases at the Centers for Disease Control and Prevention.

According to Science News, there are ways to destroy the E coli bacteria in flour using certain heat treatments. However, they are not in use in the US because they can alter the structure of the flour, which affects the texture of baked goods.

Dry climates in a desiccated state

Typically, E coli bacteria is present in wet environments like hamburger meat and leafy vegetables but the new evidence proves it can survive in dry climates in a desiccated state. 

When mixed with wet ingredients like milk, eggs and butter, it is revived and starts to replicate. 

As part of the study, Crowe added to identify exposures associated with the outbreak, outbreak cases were compared with non-STEC enteric illness cases, matched according to age group, sex, and state of residence. 

Products suspected to be related to the outbreak were collected for STEC testing, and a common point of contamination was sought. Whole-genome sequencing was performed on isolates from clinical and food samples.

Univariable exact conditional logistic-regression models of 22 matched sets showed that infection was significantly associated with the use of one brand of flour and with tasting unbaked homemade dough or batter​,” he said. 

Laboratory testing isolated the outbreak strains from flour samples, and whole-genome sequencing revealed the isolates from clinical and food samples were closely related to one another genetically​. 

Trace-back investigation identified a common flour-production facility​.” 

Source:​ The New England Journal of Medicine​. 

Title:​ Shiga Toxin–Producing E. coli​ Infections Associated with Flour. 

Authors:​ Samuel J. Crowe; Lyndsay Bottichio; Lauren N. Shade; Brooke M. Whitney; Nereida Corral; Beth Melius; Katherine D. Arends; Danielle Donovan; Jolianne Stone; Krisandra Allen; Jessica Rosner; Jennifer Beal; Laura Whitlock; Anna Blackstock; June Wetherington; Lisa A. Newberry; Morgan N. Schroeder; Darlene Wagner; Eija Trees; Stelios Viazis; Matthew E. Wise; Karen P. Neil

Date:​ November 23, 2017 

DOI:​ 10.1056/NEJMoa1615910

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