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Published on: December 23, 2022
Shiga Toxin-Producing E. coli Infections Associated with Flour
Samuel J Crowe1, Lyndsay Bottichio1, Lauren N Shade1
1From the Centers for Disease Control and Prevention (S.J.C., L.B., L.W., A.B., M.N.S., D.W., E.T., M.E.W., K.P.N.), and IHRC (L.B., D.W.), Atlanta; Food and Drug Administration, College Park, MD (L.N.S., B.M.W., J.B., S.V.); Colorado Department of Public Health and Environment, Denver (N.C.); Washington State Department of Health, Shoreline (B.M.), and Food and Drug Administration, Bothell (J.W., L.A.N.) - both in Washington; Michigan Department of Health and Human Services, Lansing (K.D.A., D.D.); Oklahoma State Department of Health, Oklahoma City (J.S.); and Virginia Department of Health, Richmond (K.A., J.R.).
Raw flour contaminated with Shiga toxin-producing Escherichia coli (STEC) caused a widespread 2016 outbreak. Tasting raw dough or batter was a key risk factor, highlighting flour
Area of Science:
- Foodborne illness epidemiology
- Microbial food safety
- Public health surveillance
Background:
- Investigation of a 2016 multi-jurisdictional outbreak linked to Shiga toxin-producing Escherichia coli (STEC) serogroups O121 and O26.
- Suspected contamination source identified as flour from a large domestic producer.
Purpose of the Study:
- To identify specific exposures associated with the STEC outbreak.
- To determine the source of STEC contamination in the food supply.
- To genetically characterize outbreak strains from clinical and food samples.
Main Methods:
- Case definition established for STEC infections with illness onset between December 21, 2015, and September 5, 2016.
- Matched case-control study comparing outbreak cases with non-STEC enteric illness controls.
- Laboratory analysis of suspected products for STEC, including whole-genome sequencing (WGS) of isolates.
- Trace-back investigation to identify the common point of contamination.
Main Results:
- Fifty-six cases of STEC infection were identified across 24 states.
- Significant associations found with the use of a specific flour brand (OR=21.04) and consumption of unbaked dough/batter (OR=36.02).
- STEC outbreak strains were isolated from flour samples; WGS confirmed genetic relatedness between clinical and food isolates.
- Trace-back investigation pinpointed a common flour production facility.
Conclusions:
- Raw flour was implicated as the definitive source of the STEC outbreak.
- This study underscores that raw flour, despite being a low-moisture food, can serve as a vehicle for foodborne pathogens.
- Highlights the importance of safe food handling practices, particularly avoiding consumption of raw flour products.
