CANADA – Investigators have unearthed a compelling link between the contamination and the aerosolization of bacteria from restaurant drainage systems during an analysis of a Canadian foodborne salmonellosis outbreak.

The revelation, stemming from an outbreak between January 1, 2020, and August 13, 2021, underscores the importance of considering unconventional risk factors in foodborne illness investigations.

The investigation, spearheaded by the Public Health Department of the Integrated University Health and Social Services Center of the Capitol of Quebec (DSPu), commenced when 67 cases of Salmonella infections were reported, with 66 percent directly traced to a local restaurant.

Intriguingly, whole genome sequencing (WGS) unveiled identical Salmonella strains among the affected individuals, pinpointing the restaurant as the epicenter.

Despite the initial inspection by the Quebec Ministry of Agriculture, Fisheries, and Food (MAPAQ) revealing no hygiene or food safety deficiencies, the elusive source persisted.

Food samples, including ready-to-eat (RTE) and raw chicken suspected to be the culprit, yielded negative results for Salmonella.

However, a breakthrough occurred during a subsequent visit when environmental samples from various surfaces and drains within the restaurant tested positive for Salmonella.

The investigators theorized persistent environmental contamination leading to foodborne transmission through aerosols.

The sampled sites, including the underside of shelves, sink drains, and floor drains, displayed intermittent Salmonella presence despite rigorous cleaning and disinfection measures by the restaurant’s management.

The replacement of the main sink and subsequent interventions proved partially effective, as certain areas exhibited recurrent contamination.

The investigation unveiled a pivotal event preceding the outbreak—a kitchen fire that prompted firefighters to employ a powder extinguisher and water jet.

The hypothesis suggests that this firefighting effort introduced Salmonella contamination to the kitchen drains, laying the groundwork for the subsequent outbreak.

Notably, despite replacing the main sink and extensive decontamination efforts, the drain in the dishwashing sink continued to test positive for Salmonella between January and March 2021.

The conclusive turning point came after all environmental samples collected post-March 25, 2021, returned negative results, marking the end of the persistent contamination.

This revelation prompts questions about the aftermath of restaurant kitchen fires, particularly when water comes into contact with food due to firefighting efforts.

The findings beckon a reconsideration of protocols, advocating for routine drain cleaning operations following such incidents to mitigate the risk of bacterial contamination and subsequent foodborne outbreaks.

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