Everything but the kitchen sink: The use of multiple hypothesis generation methods to investigate an outbreak of Salmonella Enteritidis associated with frozen profiteroles and eclairs.

In December 2018, an outbreak of Salmonella Enteritidis infections was identified in Canada by whole-genome sequencing (WGS). An investigation was initiated to identify the source of the illnesses, which proved challenging and complex. Microbiological hypothesis generation methods included comparisons of Salmonella isolate sequence data to historical domestic outbreaks and international repositories. Epidemiological hypothesis generation methods included routine case interviews, open-ended centralized re-interviewing, thematic analysis of open-ended interview data, collection of purchase records, a grocery store site visit, analytic comparison to healthy control groups, and case-case analyses. Food safety hypothesis testing methods included food sample collection and analysis, and traceback investigations. Overall, 83 cases were identified across seven provinces, with onset dates from 6 November 2018 to 7 May 2019. Case ages ranged from 1 to 88 years; 60% (50/83) were female; 39% (22/56) were hospitalized; and three deaths were reported. Brand X profiteroles and eclairs imported from Thailand were identified as the source of the outbreak, and eggs from an unregistered facility were hypothesized as the likely cause of contamination. This study aims to describe the outbreak investigation and highlight the multiple hypothesis generation methods that were employed to identify the source.

A multi-provincial outbreak of Salmonella Newport infections associated with red onions: A report of the largest Salmonella outbreak in Canada in over 20 years.

An investigation into an outbreak of Salmonella Newport infections in Canada was initiated in July 2020. Cases were identified across several provinces through whole-genome sequencing (WGS). Exposure data were gathered through case interviews. Traceback investigations were conducted using receipts, invoices, import documentation, and menus. A total of 515 cases were identified in seven provinces, related by 0-6 whole-genome multi-locus sequence typing (wgMLST) allele differences. The median age of cases was 40 (range 1-100), 54% were female, 19% were hospitalized, and three deaths were reported. Forty-eight location-specific case sub-clusters were identified in restaurants, grocery stores, and congregate living facilities. Of the 414 cases with exposure information available, 71% (295) had reported eating onions the week prior to becoming ill, and 80% of those cases who reported eating onions, reported red onion specifically. The traceback investigation identified red onions from Grower A in California, USA, as the likely source of the outbreak, and the first of many food recall warnings was issued on 30 July 2020. Salmonella was not detected in any tested food or environmental samples. This paper summarizes the collaborative efforts undertaken to investigate and control the largest Salmonella outbreak in Canada in over 20 years.

Fermenting a place in history: The first outbreak of Escherichia coli O157 associated with kimchi in Canada.

A Canadian outbreak investigation was initiated in January 2022 after a cluster of cases of Shiga-toxin-producing Escherichia coli (STEC) O157 was identified through whole genome sequencing (WGS). Exposure information was collected through case interviews. Traceback investigations were conducted, and samples from case homes, retail, and the manufacturer were tested for STEC O157. Fourteen cases were identified in two provinces in Western Canada, with isolates related by 0-5 whole genome multi-locus sequence typing allele differences. Symptom onset dates ranged from 11 December 2021 to 7 January 2022. The median age of cases was 29.5 (range 0-61); 64% were female. No hospitalisations or deaths were reported. Of 11 cases with information available on fermented vegetable exposures, 91% (10/11) reported consuming Kimchi Brand A during their exposure period. The traceback investigation identified Manufacturer A in Western Canada as the producer. One open and one closed sample of Kimchi Brand A tested positive for STEC O157, with isolates considered genetically related by WGS to the outbreak strain. Napa cabbage within the kimchi product was hypothesised as the most likely source of contamination. This paper summarises the investigation into this STEC O157 outbreak associated with kimchi, the first reported outside of East Asia.

Outbreak of Vibrio parahaemolyticus Associated with Consumption of Raw Oysters in Canada, 2015.

There has been a steady increase in illness incidence of Vibrio parahaemolyticus (Vp). The majority of illnesses are associated with consumption of raw oysters. In the summer of 2015, Canada experienced the largest outbreak associated with the consumption of raw oysters harvested from British Columbia (BC) coastal waters. Case investigation of laboratory-confirmed cases was conducted to collect information on exposures and to assist traceback. Investigations at processors and oyster sampling were conducted. Eighty-two laboratory-confirmed cases of Vp infection were reported between January 1 and October 26, 2015. The majority of the cases were reported in BC, associated with consumption of raw BC oysters in restaurants. Sea surface temperatures were above the historical levels in 2015. This outbreak identified the need to improve surveillance and response to increases in human cases of Vp. This is of particular importance due to the potential for increasing water temperatures and the likelihood of additional outbreaks of Vibrio.

A multi-provincial Salmonella Typhimurium outbreak in Canada associated with exposure to pet hedgehogs, 2017-2020.

Background: In October 2020, an investigation began in Canada on an outbreak of Salmonella Typhimurium infections of the same strain as a concomitant outbreak in the United States (US) that was linked to pet hedgehogs. The objective of this article is to identify the source of the outbreak, determine if there was a link between the Canadian and US outbreaks and identify risk factors for infection to inform public health interventions. Methods: Cases were identified through whole genome sequencing of S. Typhimurium isolates. Information was collected on case exposures, including animal contact. Hedgehog and environmental specimens were tested for S. Typhimurium and a trace back investigation was conducted. Results: There were 31 cases in six provinces, with illness onset dates from June 1, 2017, to October 15, 2020. Median case age was 20 years and 52% were female. Isolates grouped together between 0-46 whole genome multi locus sequence typing allele differences. Of 23 cases with available exposure information, 19 (83%) reported contact with hedgehogs in the seven days prior to symptoms; 15/18 (83%) reported direct contact and 3/18 (17%) reported indirect contact. Trace back investigation did not identify a common source of hedgehogs but uncovered an industry with a complex distribution network. The outbreak strain was detected in samples collected from a hedgehog in one case's home and from a hedgehog in a Québec zoo. Conclusion: Direct and indirect contact with hedgehogs was identified as the source of this S. Typhimurium outbreak. Public health communications aimed to increase awareness about the risks of zoonoses from hedgehogs and shared key hygienic practices to reduce disease transmission.

Outbreak of Escherichia coli O157:H7 Infections Linked to Mechanically Tenderized Beef and the Largest Beef Recall in Canada, 2012.

Contaminated beef is a known vehicle of Escherichia coli O157:H7 infection, although more attention is given to the control of E. coli O157:H7 in ground, rather than whole-cut, beef products. In September 2012, an investigation was initiated at an Alberta, Canada, beef plant after the detection of E. coli O157:H7 in two samples of trim cut from beef originating from this plant. Later in September 2012, Alberta Health Services identified five laboratory-confirmed infections of E. coli O157:H7, and case patients reported eating needle-tenderized beef steaks purchased at a store in Edmonton, Alberta, produced with beef from the Alberta plant. In total, 18 laboratory-confirmed illnesses in Canada in September and October 2012 were linked to beef from the Alberta plant, including the five individuals who ate needle-tenderized steaks purchased at the Edmonton store. A unique strain of E. coli O157:H7, defined by molecular subtyping and whole genome sequencing, was detected in clinical isolates, four samples of leftover beef from case patient homes, and eight samples of Alberta plant beef tested by industry and food safety partners. Investigators identified several deficiencies in the control of E. coli O157:H7 at the plant; in particular, the evaluation of, and response to, the detection of E. coli O157 in beef samples during routine testing were inadequate. To control the outbreak, 4,000 tons of beef products were recalled, making it the largest beef recall in Canadian history. This outbreak, in combination with similar outbreaks in the United States and research demonstrating that mechanical tenderization can transfer foodborne pathogens present on the surface into the interior of beef cuts, prompted amendments to Canada's Food and Drug Regulations requiring mechanically tenderized beef to be labeled as such and to provide safe cooking instructions to consumers. A detailed review of this event also led to recommendations and action to improve the safety of Canada's beef supply.

Outbreak of Escherichia coli O157:H7 Infections Linked to Aged Raw Milk Gouda Cheese, Canada, 2013.

Between 12 July and 29 September 2013, 29 individuals in five Canadian provinces became ill following infection with the same strain of Escherichia coli O157:H7 as defined by molecular typing results. Five case patients were hospitalized, and one died. Twenty-six case patients (90%) reported eating Gouda cheese originating from a dairy plant in British Columbia. All of the 22 case patients with sufficient product details available reported consuming Gouda cheese made with raw milk; this cheese had been produced between March and July 2013 and was aged for a minimum of 60 days. The outbreak strain was isolated from the implicated Gouda cheese, including one core sample obtained from an intact cheese wheel 83 days after production. The findings indicate that raw milk was the primary source of the E. coli O157:H7, which persisted through production and the minimum 60-day aging period. This outbreak is the third caused by E. coli O157:H7 traced to Gouda cheese made with raw milk in North America. These findings provide further evidence that a 60-day ripening period cannot ensure die-off of pathogens that might be present in raw milk Gouda cheese after production and have triggered an evaluation of processing conditions, physicochemical parameters, and options to mitigate the risk of E. coli O157:H7 infection associated with raw milk Gouda cheese produced in Canada.