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E. coli EHEC - Canada (11): O121, flour

PRO/AH/EDR> E. coli EHEC - Canada (11): O121, flour [EXTERNAL]
Date: 7 luglio 2017 02:42:53 CEST
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A ProMED-mail post <> ProMED-mail is a program of the International Society for Infectious Diseases <>

Date: Thu 7 Jul 2017
Source: Source: CDC. MMWR Morb Mortal Wkly Rep 2017;66(26): 705-706 [edited] <>

On 29 Dec 2016, PulseNet Canada identified a cluster of 6 _Escherichia coli_ non-O157 isolates with a matching pulsed-field gel electrophoresis (PFGE) pattern combination that was new to the PulseNet Canada database. The patients resided in 3 geographically distinct provinces. In January 2017, the Public Health Agency of Canada (PHAC) initiated an investigation with local, provincial, and federal partners to investigate the source of the outbreak.

A case was defined as isolation of _E. coli_ non-O157 with the outbreak PFGE pattern or closely related by whole genome sequencing (WGS) in a Canadian resident or visitor with onset of symptoms of gastroenteritis on or after 1 Nov 2016. Patients' illness onset dates ranged from November 2016 to April 2017 [Figure - for figure, see original URL - Mod.LL]. As of 23 May 2017, a total of 29 cases were identified in 6 provinces (Alberta, British Columbia, Newfoundland and Labrador, Ontario, Quebec, and Saskatchewan). One additional case was identified in a U.S. resident who traveled to Canada during the exposure period. Patients' ages ranged from 2-79 years (median = 23.5 years) and 50 percent were female. Eight patients were hospitalized, and one developed hemolytic uremic syndrome. Clinical isolates were typed as _E. coli_ O121:H19 (one case was typed as _E. coli_ O121:H undetermined) with Shiga toxin 2-producing genes by in silico toxin testing and had closely related PFGE patterns and WGS.

Initial investigation into the source of the outbreak did not identify any clear hypotheses; common exposures were ground beef, sausage style deli-meats, pizza, and pork, but the data did not converge on any specific products. Patients were reinterviewed by PHAC using an open-ended approach. Knowledge of a recent _E. coli_ O121 flour-associated outbreak prompted interviewers to ask about baking and exposure to raw flour or dough (1). Patients were also asked if any food items of interest, including flour, were available for testing.

In March 2017, _E. coli_ O121 with the outbreak PFGE pattern was isolated from an open flour sample from a patient's home and a closed sample collected at a retail store, both of the same brand and production date. The clinical and flour isolates grouped together, with only 0-6 whole genome multilocus sequence typing allele differences. As a result of these findings, a product recall was issued. Based on possible connections to the recalled lot of flour, market sampling of flour within certain periods was initiated. The investigation led to additional recalls of flour and many secondary products (2).

As of 23 May 2017, 22 patients had been asked about flour exposure in the 7 days before illness onset; 16 (73 percent) reported that the implicated brand of flour was used or probably used in the home during the exposure period. Comparison data on the expected proportion with exposure to this brand of flour were not available. Up to 11 of these 16 patients reported they ate or probably ate raw dough during their exposure period.

This is the 1st national outbreak of non-O157 Shiga toxin-producing _E. coli_ infections identified in Canada and the 1st Canadian outbreak linked to flour. An open-ended interview approach and flour sampling were used to implicate flour as the source. Because of the recent emergence of _E. coli_ outbreaks linked to flour, public health professionals should consider flour as a possible source in _E. coli_ outbreaks and communicate the risk associated with exposure to flour, raw batter, and dough in public health messaging.

1. CDC: Multistate outbreak of Shiga toxin-producing Escherichia coli infections linked to flour (Final Update). Atlanta, GA: US Department of Health and Human Services, CDC; 2016.
2. Canadian Food Inspection Agency: Canadian Food Inspection Agency's (CFIA) investigation into E. coli O121 in flour and flour products. Mississauga, Canada: Canadian Food Inspection Agency; 2017.

[Authors: Morton V, Cheng JM, Sharma D, Kearney A]

Communicated by: ProMED-mail <>

[As reported by Canadian authorities, Isolates from the 2016 US O121 outbreak have been compared to the outbreak in Canada by whole genome sequencing (via PulseNet International); the Canadian outbreak strain was not similar to the US outbreak.

As a reminder, other non-O157 _E. coli_ serogroups that have been associated with EHEC disease include motile ones such as O26:H11 and O104:H21 and non-motile ones such as O111:NM (or H-). Such non-O157 isolates can be obtained from sheep and cattle, and although they cause as many as 30 percent of outbreaks of EHEC (1), they appear to be somewhat less (or at least more variably) virulent in a variety of in vivo and in vitro assays (2-4). In analyzing the genetic and phenotypic profiles of non-O157 groups, it has been found that they belong to their own lineages and have unique profiles of virulence traits different from O157 (5). The serogroups appearing to be most prominent are O26, O111, O128, and O103 (6).

1. Hussain HS, Omaye ST. Introduction to the food safety concerns of verotoxin-producing _Escherichia coli_. Exp Biol Med. 2003; 228:331-2.
2. Blanco J, Blanco M, Blanco JE, et al. Verotoxin-producing _Escherichia coli_ in Spain: prevalence, serotypes, and virulence genes of O157:H7 and non-O157 VTEC in ruminants, raw beef products, and humans. Exp Biol Med. 2003; 228: 345-51.
3. Law D, Kelly J. Use of heme and hemoglobin by _Escherichia coli_ O157 and other Shiga-toxin-producing _E. coli_ serogroups. Infect Immun. 1995; 63: 700-2.
4. Tzipori S, Wachsmuth KI, Smithers J, Jackson C. Studies in gnotobiotic piglets on non-O157:H7 _Escherichia coli_ serotypes isolated from patients with hemorrhagic colitis. Gastroenterology 1988; 94: 590-7.
5. Schmidt H, Geitz C, Tarr PI, et al. Non-O157:H7 pathogenic Shiga-toxin producing _Escherichia coli_: phenotypic and genetic profiling of virulence traits and evidence for clonality. J Infect Dis. 1999; 179: 115-23.
6. Bettelheim KA. Role of non-O157 VTEC. Symp Ser Soc Appl Microbiol. 2000; (29): 38-50S. - Mod.LL

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[See Also:

E. coli EHEC - Canada (10): (BC) O121, flour
E. coli EHEC - Canada (09): O121, flour, further recalls
E. coli EHEC - Canada (08): O121, flour
E. coli EHEC - Canada (07): O121, flour, wider recall
E. coli EHEC - Canada (06): O121, flour, expanded recall
E. coli EHEC - Canada (05): O121, flour
E. coli EHEC - Canada (04): O121, flour
E. coli EHEC - Canada (03): O121
E. coli EHEC - Canada (02): O121, RFI
E. coli EHEC - Canada: O121

E. coli EHEC - USA (25): O121, O26, flour, alert, expanded recall
E. coli EHEC - Canada: (AB) O157
E. coli EHEC - USA (16): O121, flour, alert, recall
E. coli EHEC - USA (14): O121, flour, alert, recall

E. coli EHEC - Canada (04): O157
E. coli EHEC - Canada (03): O157
E. coli EHEC - Canada (02): (ON) O157, leafy greens susp, correction
E. coli EHEC - Canada (02): (ON) O157, leafy greens susp
E. coli EHEC - Canada: O157

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Published 16-01-2017 in Focus on , last update 07-07-2017


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