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2012-2014 Bacterial Pathogens and Generic E. Coli in Green Onions


Targeted surveys are used by the Canadian Food Inspection Agency (CFIA) to focus its surveillance activities on areas of highest health risk. The information gained from these surveys provides both support for the prioritization of the Agency's activities to areas of greater concern, and scientific evidence to address areas of lesser concern. Originally started under the Food Safety Action Plan (FSAP), targeted surveys have been incorporated into the CFIA's regular surveillance activities as a valuable tool for generating information on certain hazards in foods, identifying/characterizing new and emerging hazards, informing trend analysis, prompting/refining health risk assessments, highlighting potential contamination issues, as well as assessing and promoting compliance with Canadian regulations.

Green onions have been reported to be responsible for several outbreaks of foodborne illness in North America. Often eaten raw, green onions are subject to extensive handling during and after harvest, where pathogens can be introduced at any step of production. Furthermore, their hollow structure provides favorable conditions for pathogen growth and protection from washing. The Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO) has ranked green onions in the second highest priority group of concern for microbiological hazards in fresh fruits and vegetables.

Considering these factors and their relevance to Canadians, green onions have been selected as one of the priority commodity groups of fresh fruits and vegetables for enhanced surveillance. Over the course of a four-year baseline study (2010/11 to 2013/14), approximately 4,500 green onion samples were collected from retail locations and tested for the presence of various pathogens of concern. Results of the first two years of the study (2010-2011 & 2011-2012) can be found at and respectively.

The main objectives of these targeted surveys (2012/13 – 2013/14) were to generate baseline surveillance data on the bacterial pathogens Salmonella, Shigella, and Escherichia coli (E. coli) O157:H7/NM (non-motile), as well as on generic E. coli, an indicator of fecal contamination, in green onions available in the Canadian market. In total, 2,903 samples of green onions (imported and domestic, conventionally and organically grown) were collected and analyzed. Most samples (99.7%) were assessed as satisfactory. Eight samples were assessed as unsatisfactory: one for the presence of Salmonella and seven for high levels of generic E. coli (>1,000 Most Probable Number/gram (MPN/g)). Subsequent food safety investigations resulted in one product recall. In addition, two samples were assessed as investigative for elevated, yet marginally acceptable levels of generic E. coli (100 – 1,000 MPN/g). Further evaluation of these samples resulted in no immediate follow-up action. These findings suggest that the green onions sampled from the Canadian market over the course of this survey were predominantly produced under Good Agricultural Practices (GAPs) and Good Manufacturing Practices (GMPs).

The CFIA regulates and provides oversight to the industry, works with provinces and territories, and promotes the safe handling of foods throughout the food production chain. However, it is important to note that the food industry and retail sectors in Canada are ultimately responsible for the food they produce and sell, while individual consumers are responsible for the safe handling of the food they have in their possession. Moreover, general advice for the consumer on the safe handling of foods is widely available. The CFIA will continue its surveillance activities and will inform stakeholders of its findings.

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