by Gigi de Fort-Menares Lee, Gabriel Pineda, and Victoria Tseng Paepcke

Introduction:

On May 25, 2019, the Public Health Agency of Canada declared a national Salmonella outbreak linked to Compliments Chicken Strips. Currently, there have been 11 reported cases across 7 different provinces between September 2018 and April 2019. One individual has been hospitalized and no deaths have been reported due to this outbreak.  As well, the suspected source has been identified. Unfortunately, there have been a multitude of outbreak investigations associated with frozen raw breaded chicken products and Salmonella since May 2017. 

Description of the Disease:

Salmonella is a genus of Gram-negative, rod-shaped, facultative anaerobic bacterium (See Figure 1). The outbreaks caused by frozen raw breaded chicken are linked to Salmonella enteritidis (S. enteritidis), the most common serotype in Canada. S. enteritidis is an intracellular pathogen which causes the disease salmonellosis. Due to its prevalence, it is one of the most important zoonotic diseases and frequently is transmitted to humans through the consumption of raw animal products such as poultry meat and eggs. Interestingly, these bacteria prefer the intestinal tract of animals as their environment but can persist for a long period of time in other environments by forming biofilms. To clarify, biofilms are generally a mass of bacteria that are held within a gel-like structure. After ingestion, the stomach’s acidity degrades the meat and the pathogen multiplies in the small intestine before establishing infection. 

Symptoms of salmonellosis depend largely on the species and/or serovar of bacterium. For S. enteritidis, symptoms include diarrhea, vomiting, abdominal pain, fever, chills and headache. The onset of symptoms appears 6 to 72 hours after ingestion of the bacteria and illness typically lasts 2 to 7 days. Most cases of salmonellosis are relatively mild and patients will make a full recovery without treatment. However, children and elderly patients are more susceptible to the associated dehydration which can lead to a more serious or even life-threatening illness. Antibiotics are only administered to infants, the elderly, immunocompromised people or if the infection has spread to other parts of the body. Furthermore, antibacterial therapy is not recommended in moderate cases because increased use of antibiotics accelerates the evolution of bacterial strains by allowing these strains to pick up new factors which consequently could lead to drug resistance. Unfortunately, several resistant serotypes of Salmonella have arisen and antibacterial resistance is thus a growing concern. 

Source of the Outbreak:

Several outbreaks of S. enteritidis have occurred in Canada over the years. As mentioned, the most recent outbreak of the bacteria was reported on May 25, 2019.  The outbreak originated from chicken strips sold under the brand “Compliments” from Sofina Foods Inc. The Public Health Agency of Canada reported 11 cases of infection nationwide: 2 in British Columbia, 1 in Alberta, 2 in Ontario, 3 in Quebec, 1 in New Brunswick, 1 in Nova Scotia and 1 in Prince Edward Island. Furthermore, other cases of salmonellosis have arisen in Canada. For instance, in March 2019, 34 cases related to frozen raw breaded chicken were reported with the majority of cases occurring in Ontario (22). The Canadian Food Inspection Agency (CFIA) investigated the sources of outbreaks of S. enteritidis and posted a list of products that had tested positive for the bacteria from outbreaks dating back to 2017. 

*  Table has been modified from the original table compiled by the CFIA. Source: List of recalls of frozen raw breaded chicken products due to Salmonella: from July 2017 to present. 2019. Ottawa (ON): Government of Canada; [accessed 2019 Nov 10]. http://inspection.gc.ca/about-the-cfia/accountability/food-safety-investigations/raw-breaded-chicken-products/eng/1536716947924/1536717030715

Cause of the Outbreak: 

According to the Public Health Agency of Canada, outbreaks of S. enteritidis can be caused by contact with infected animals and surfaces and ingestion of contaminated food (See Figure 2). Interestingly, S. enteritidis infection is especially a problem among poultry, as the bacteria colonize the reproductive tract of hens. Thus, the interior of eggs become colonized prior to shell formation. Furthermore, chickens occasionally ingest either their own or other chickens’ feces that may contain the pathogen promoting transmission. Accordingly, ingestion of contaminated food is the cause of the outbreak under discussion as the frozen raw breaded chicken contained the pathogen. In 2009, Dominguez and Schaffner demonstrated that S. enteritidis is able to survive under freezing conditions (- 20 °C) for almost 16 weeks explaining why frozen food is a source of outbreak. Moreover, infected individuals do not cook the meat properly, allowing the bacteria to survive.  Other causes of contamination include unsanitary distribution management and antibiotic resistance. Antibiotic resistance is partially responsible for S. enteritidis outbreaks as with increased resistance, there are more cases of salmonellosis which consequently increases the risk of an outbreak to occur. Interestingly, in 2018, Nair et al. explained that after the approval and increased usage of fluoroquinolones, serotypes acquired resistance to the antibiotic. In support of this claim, they showed a positive correlation between cases of Salmonella Heidelberg infection in Canada and antibiotic resistance. Overall, several factors contributed to the initiation of the S. enteritidis outbreak.

Figure 2: Possible routes of S. enteritidis transmission to humans. Source: Victoria Tseng Paepcke (2019).

Measures Taken to End Outbreak:

In order to end the outbreak, Compliments Chicken Strips with a best before date of November 24, 2019 were recalled on May 24, 2019.  Although no longer available in stores, this product may be found in freezers of homes or restaurants.  Consequently, the Government of Canada (GC) advises the public not to consume nor sell the recalled product and to seal the product in a plastic bag and either dispose of it or return it to where it was purchased. 

Canadian chicken farms and processing plants must routinely disinfect their facilities in order to prevent S. enteritidis outbreaks from raw breaded chicken, as the facilities may experience contamination from either the live or frozen chickens. Farmers must also routinely check for S. enteritidis within their flock and ensure that birds are handled using sanitary procedures. Actions to eliminate the bacteria at the production level aid in reducing cases among consumers.

If consumers are infected with S. enteritidis, treatment by fluids, electrolytes, anti-diarrheals and antibiotics may be recommended.  Fluids and electrolytes are used to replenish body fluids as infection can cause dehydration.  Anti-diarrheals may be used to relieve symptoms such as cramping and diarrhea.  As previously mentioned, if a person has either a severe case of intestinal infection, bloodstream infection or a compromised immune system, he or she may be prescribed antibiotics.

Aftermath:

S. enteritidis in breaded chicken has a better chance of infecting people because of the golden coating of the nuggets or strips that appears cooked.  Thus, the GC has enforced safe cooking practices in order to reduce potential infections.  For example, the GC suggests that all frozen raw breaded chicken products should be cooked to an internal temperature of 74°C and microwave cooking is not recommended due to uneven heating.  Thus, actions to reduce S. enteritidis cases can be performed by a range of parties, from individual citizens to the GC.

Due to numerous outbreaks like the one discussed, stricter standards have been implemented. Starting April 1, 2019, the CFIA stated that all breaded chicken manufacturers need to reduce S. enteritidis levels to below detectable amounts.  In other words, most chicken products will be pre-cooked. Also, “uncooked products” must be stated clearly on the packaging and cooking instructions must be present on both the box and internal bag. Overall, regulations have been changed with the hope of preventing future S. enteritidis outbreaks.

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