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2011-2012 Bacterial Pathogens and Generic E. coli in Leafy Vegetables


The Food Safety Action Plan (FSAP) aims to modernize and strengthen Canada's food safety system in order to better protect Canadians from unsafe food and ultimately reduce the occurrence of foodborne illness.

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. The bacterial pathogens Escherichia coli (E. coli) O157:H7 and Salmonella have accounted for the majority of the outbreaks associated with leafy vegetables. Shigella and Campylobacter have also been implicated in leafy vegetables associated outbreaks. In addition, Listeria monocytogenes (L. monocytogenes) has been identified as a food safety concern in ready-to-eat (RTE) foods including fresh-cut RTE leafy vegetables due to its wide distribution in the environment and its ability to grow under refrigeration temperatures.

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 under the FSAP. Over the course of a five-year baseline study (2008/09 - 2012/13), approximately 10,000 leafy vegetable samples were collected from Canadian retail locations and tested for various pathogens of concern. The main objectives of the 2011/12 survey were to generate baseline surveillance data on bacterial pathogens E. coli O157, Salmonella, Shigella, Campylobacter, and Listeria monocytogenes, 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 1537 imported and domestic samples, including 320 whole leafy vegetable samples and 653 fresh-cut leafy vegetable samples, were collected and tested for the targeted bacteria. Bacterial pathogens E. coli O157, Salmonella, Shigella, and Campylobacter were not detected in any of the samples. One of the fresh-cut samples (0.2%) was found to have an elevated, yet marginally acceptable, level of generic E. coli. Generic E. coli is an indicator used by the Canadian Food Inspection Agency (CFIA) to assess general sanitation and hygiene practices throughout the production chain. Two of the fresh-cut samples (0.3%) were assessed as unsatisfactory due to the presence of L. monocytogenes. Since the products were already passed their stated shelf-life when the results were confirmed, there were no related products recalled. The CFIA conducted appropriate follow-up activities for the contaminated products, including a joint inspection with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) at one of the processing facility. No reported illnesses were found to be associated with the contaminated products during this survey. 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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