Investigation of 2020 Salmonella Outbreak in Restaurant Finds Drain Contamination as Likely Source for Ongoing Issues

An investigative report in the Journal of Food Protection provides the approach and findings related to a 2020 Salmonella outbreak which "identified a total of 67 cases between January 1, 2020, and August 13, 2021, 66% of which were directly linked to a restaurant in the area".   Regulatory officials conducted a intensive investigation, looking at many angles, but in the end, they believe the endemic contamination was linked to the kitchen drainage system.

"Explanatory hypothesis adopted. The most plausible explanation for the origin of this outbreak remains the contamination of the drains in Restaurant A. Indeed, most of the environmental samples positive for Salmonella were found in sinks or near them (sink sprayers, drains). The presence of contaminated biofilm (Mair-Jenkins et al., 2017) in the restaurant’s kitchen drainage system may have had a role to play in the extended duration of this outbreak."

A few takeaways:

• The importance of periodic drain cleaning. This occurs in food operations, but not really discussed to any degree for foodservice operations. Depending on the location of the drain relative to operational areas and the potential for the drains backing up, the risk of contamination from drains can vary. However, a periodic cleaning regiment can reduce this risk.
• During investigations,  much focus is placed on a given food item.  In this case, an environmental niche may have been the source to many food items via contaminated equipment or hands.  These out-of-site niche areas can foster resident or endemic contamination that can be difficult to identify if only looking at given food items.

Journal of Food Protection
https://www.sciencedirect.com/science/article/pii/S0362028X23068151?via%3Dihub
Research Paper
Investigation of a Salmonella Montevideo Outbreak Related to the Environmental Contamination of a Restaurant Kitchen Drainage System, Québec, Canada, 2020–2021

Author links open overlay panelAndré Paradis 1 †, Marie-France Beaudet 1 †, Marianne Boisvert Moreau 2 †, Caroline Huot 3 †
Abstract


In May 2020, the Direction de santé publique du CIUSSS de la Capitale-Nationale (DSPu) received a report from the Laboratoire de santé publique du Québec of a cluster of three cases of Salmonella enterica enterica, serogroup C1, serotype Montevideo. The epidemiological investigation identified a total of 67 cases between January 1, 2020, and August 13, 2021, 66% of which were directly linked to a restaurant in the area. The Salmonella strains from most of these cases were found to be identical by whole-genome sequencing (cluster code 2005MontWGS-1QC). The initial inspection of the restaurant by the competent authorities (Ministère de l’agriculture, des pêcheries et de l’alimentation du Québec) – including the evaluation of hygiene and food safety, the search for cases of illness among workers and food sampling – was unable to establish the source of the outbreak. Environmental samples showed that the restaurant’s kitchen drains were contaminated with the same strain of Salmonella Montevideo as the cases in the outbreak. Several cleaning and disinfection methods were used repeatedly. When environmental sampling at the restaurant sites was repeatedly and consecutively negative, cases in the community stopped. The prior occurrence of a fire in the kitchen may have played a role in the contamination of the restaurant drains. In conclusion, public health professionals should consider drainage systems (plumbing) and possible aerosolization of bacteria as a potential source of a restaurant-related salmonellosis outbreak.