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2012-2014 Bacterial Pathogens and Generic E. Coli in Leafy Vegetables


Targeted surveys are used by the Canadian Food Inspection Agency (CFIA) to focus its surveillance activities on areas of highest 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 essential information on certain hazards in foods, identifying/characterizing new and emerging hazards, informing trend analysis, prompting/refining human health risk assessments, highlighting potential contamination issues as well as assessing and promoting compliance with Canadian regulations.

In recent years, leafy vegetables have been reported to be associated with numerous outbreaks of foodborne illness worldwide. The Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO) has ranked leafy vegetables as the highest priority of concern in terms of microbiological hazards among fresh fruits and vegetables. Leafy vegetables can become contaminated with various foodborne pathogens during production, harvest, post-harvest handling, processing, packaging and distribution. Due to their leafy nature, these vegetables are more easily contaminated than others. As they are often consumed raw, the presence of pathogens creates a potential risk for foodborne illness.

Considering the factors mentioned above and their relevance to Canadians, leafy vegetables have been selected as one of the priority commodity groups of fresh fruits and vegetables for enhanced surveillance. Over the course of a baseline study between the 2008/09 and 2013/14 fiscal years, approximately 12,000 leafy vegetable samples were collected from Canadian retail locations and tested for various pathogens of concern.

The main objectives of the 2012/13 and 2013/14 surveys were to generate baseline surveillance data on bacterial pathogens Escherichia coli (E. coli) O157:H7/NM (non-motile), Salmonella, Shigella, Campylobacter, Listeria monocytogenes (fresh-cut only) and Verotoxin-producing E. coli (VTEC) (fresh-cut only), as well as on an indicator of fecal contamination, generic E. coli, for a variety of leafy vegetables available in the Canadian market. A total of 2,977 fresh leafy vegetable samples, including whole and fresh-cut samples, were collected and tested for the targeted bacteria. Most samples (99.5%) were assessed as satisfactory. One of the fresh-cut samples (0.1%) was found to be contaminated with L. monocytogenes. The CFIA conducted appropriate follow-up activities for the contaminated product, including a product recall. No reported illnesses were found to be associated with the contaminated products identified during this survey. In addition, four samples had high levels (>1,000 Most Probable Number (MPN)/g) of generic E. coli and six samples had elevated, yet marginally acceptable levels (100 – 1,000 MPN/g) of generic E. coli. Further evaluations of these samples resulted in no immediate follow-up activities. Generic E. coli is an indicator used by the CFIA to assess general sanitation and hygiene practices throughout the production chain. These results suggest that the vast majority of fresh leafy vegetables in the Canadian market sampled during this survey were produced under Good Agricultural Practices (GAPs) and Good Manufacturing Practices (GMPs). Sporadically, L. monocytogenes contamination in fresh-cut leafy vegetables can occur.

The CFIA regulates and provides oversight to the industry, works with provinces and territories, and promotes 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. In addition, general advice for the consumer on the safe handling of foods is widely available. The CFIA will continue its surveillance activities and inform stakeholders of its findings.

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