<i>Notes from the Field:</i> Multistate Outbreak of <i>Escherichia coli</i> O157:H7 Infections Linked to Dough Mix — United States, 2016

Gieraltowski, Laura; Schwensohn, Colin; Meyer, Stéphanie; Eikmeier, Dana; Medus, Carlota; Sorenson, Alida; Forstner, Matthew; Madad, Asma; Blankenship, Joseph; Feng, Peter; Williams, Ian T.

doi:10.15585/mmwr.mm6603a6

Cited by 26 publications

(19 citation statements)

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“…1,2 However, flour was not definitively identified as the source of infection in that outbreak or in subsequent outbreaks of STEC infection. Flour is a raw, minimally processed product intended to be mixed with other ingredients and cooked before consumption.…”

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confidence: 99%

Shiga Toxin–Producing E. coli Infections Associated with Flour

Crowe¹,

Bottichio²,

Shade

et al. 2017

N Engl J Med

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BACKGROUND In 2016, a multijurisdictional team investigated an outbreak of Shiga toxin–producing Escherichia coli (STEC) serogroup O121 and O26 infections linked to contaminated flour from a large domestic producer. METHODS A case was defined as infection with an outbreak strain in which illness onset was between December 21, 2015, and September 5, 2016. 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. RESULTS A total of 56 cases were identified in 24 states. Univariable exact conditional logistic-regression models of 22 matched sets showed that infection was significantly associated with the use of one brand of flour (odds ratio, 21.04; 95% confidence interval [CI], 4.69 to 94.37) and with tasting unbaked homemade dough or batter (odds ratio, 36.02; 95% CI, 4.63 to 280.17). Laboratory testing isolated the outbreak strains from flour samples, and whole-genome sequencing revealed that the isolates from clinical and food samples were closely related to one another genetically. Trace-back investigation identified a common flour-production facility. CONCLUSIONS This investigation implicated raw flour as the source of an outbreak of STEC infections. Although it is a low-moisture food, raw flour can be a vehicle for foodborne pathogens.

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confidence: 99%

Shiga Toxin–Producing E. coli Infections Associated with Flour

Crowe¹,

Bottichio²,

Shade

et al. 2017

N Engl J Med

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“…Similarly, outbreaks of O26 STEC infections associated with wheat flour occurred in the US in 2018-19 (17) and 2015-16 (18). Outbreaks of O157 STEC infections in the US associated with cookie dough (pasteurized egg) in 2009 (16,38) and dough mix in early 2016 (22) were reported.…”

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confidence: 99%

Microbiological Survey of Wheat Flour Sold at Retail in Canada, 2018 to 2019

Zhang

Yamamoto

Murphy

et al. 2021

Journal of Food Protection

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Following two O121 STEC outbreaks linked to wheat flour, this study was conducted to gain baseline information on the occurrence of bacterial pathogens and levels of indicator organisms in wheat flour in Canada. A total of 347 pre-packaged wheat flour samples were analyzed for Salmonella spp., Shiga Toxin-Producing Escherichia coli (STEC), Listeria monocytogenes ( L. monocytogenes ) , aerobic colony count (ACC), total coliforms, and generic Escherichia coli ( E. coli ) . Salmonella spp. and O157 STEC were not detected in any of the samples. L. monocytogenes was identified in two samples (0.6%) at levels below the limit of detection (<0.7 log CFU/g). Non-O157 STEC were isolated from six samples (1.7%) and were characterized for the presence of STEC virulence genes: stx 1, stx 2 and subtypes, eae , hlyA, and aggR . One O103:H25 STEC isolate carried virulence genes ( stx 1 a + eae ) that are known to be capable of causing diarrhea and/or bloody diarrhea in humans. Of the five remaining non-O157 STEC isolates, four carried single stx 2a or stx 2c genes and were considered to have the potential of causing diarrhea. The remaining non-O157 STEC isolate ( stx 2 ), while not a priority non-O157 STEC was not available for sequencing and thus its potential to cause illness is unknown. ACC, total coliforms, and generic E. coli were detected in 98.8%, 72.6% and 0.6% of the flour samples. The mean counts of ACC were greater in whole-wheat flour as compared to the other flour types tested ( p <0.001). The results of this study suggest that the occurrence of O157 STEC and Salmonella is low, but the occurrence of non-O157 STEC in wheat flour with the potential to cause human illness of diarrhea is relatively common. Therefore, the consumption of raw flour could increase the likelihood of STEC infections. Further research is merited for potential risk mitigation strategies within the food production system and with consumers.

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“…Since 2016, reports of the presence of STEC in contaminated flour have been published (CDC 2016;Gieraltowski et al 2017;Wu et al 2017). A U.S. company initiated a voluntary recall of wheat flour and products contaminated with STEC O121 and O26 (CDC 2016).…”

Section: Introductionmentioning

confidence: 99%

“…In the US, 53% of young adults ate homemade cookie dough (Byrd-Bredbenner et al 2008). In addition, flour is often used to dust surfaces for the transfer of bakery products and pizzas (Gieraltowski et al 2017). Thicker dough could be undercooked at some locations.…”

Section: Introductionmentioning

confidence: 99%

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Detection and isolation of Shiga-Toxin producing Escherichia coli in flour in Germany between 2014 and 2017

Mäde

Geuthner

Imming

et al. 2017

J Consum Prot Food Saf

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Official control samples of wheat and rye flour were analyzed for the presence of Shiga-toxin producing Escherichia coli (STEC) in 25 g. The detection procedure was based on enrichment in buffered peptone water and Tryptone Bile X-Glucuronide agar, followed by multiplex real-time PCR with an internal positive control. Positive samples were sub-cultured for strain isolation by a two-step procedure. In the first step, ten colonies were picked from each plate, pooled, and analyzed by real-time PCR. In addition, a bacterial material from the part with heavy growth was analyzed. If the 1st isolation attempt failed, in a second step all colonies from molecular positive plates were picked, sub-cultured, pooled and analyzed. 39% of test samples were positive by real-time PCR. STEC was isolated from 17 test samples corresponding to 19%. Molecular detection is linked to the presence of quantifiable numbers of E. coli, whereas the grain species did not have an influence. There is a non-significant correlation with some mills indicating some technological or hygienic problems in those facilities. Increasing the number of subsamples did improve the detection rate. Our findings show the frequent presence of STEC in flour in Germany.

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Notes from the Field: Multistate Outbreak of Escherichia coli O157:H7 Infections Linked to Dough Mix — United States, 2016

Cited by 26 publications

References 3 publications

Shiga Toxin–Producing E. coli Infections Associated with Flour

Shiga Toxin–Producing E. coli Infections Associated with Flour

Microbiological Survey of Wheat Flour Sold at Retail in Canada, 2018 to 2019

Detection and isolation of Shiga-Toxin producing Escherichia coli in flour in Germany between 2014 and 2017

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