Bacterial Pathogens and Indicators in Fresh Baby Leafy Vegetables – April 1, 2018 to March 31, 2021
Food microbiology – Targeted surveys – Final report
Summary
A 3-year targeted survey analysed 3172 samples of baby leafy vegetables for the presence of the pathogens Listeria monocytogenes (L. monocytogenes), Salmonella species (spp.), and Escherichia coli (E. coli) O157. All samples were also tested for generic E. coli which is an indicator of the hygienic and sanitary conditions of the food supply chain from production to the point of sale.
Over 99.5% of the samples tested were found to be satisfactory. Salmonella spp. and E. coli O157 were not found in any samples. L. monocytogenes was found in 12/3172 (0.38%) samples. Generic E. coli at elevated levels were found in 3/3172 (0.09%) samples. The Canadian Food Inspection Agency (CFIA) conducted appropriate follow-up activities. There were no reported illnesses related to these products.
Overall, our survey results indicate that baby leafy vegetables sold in Canada are generally safe for consumption, however they can occasionally be contaminated. Consequently, as with all foods, and especially with those that are consumed raw, good hygienic practices are recommended for producers, retailers and consumers.
Why was this survey conducted
The survey was conducted to generate baseline information on the quality and safety of fresh baby leafy vegetables sold at retail in Canada.
Baby leafy vegetables are younger versions of typical leafy greens such as spinach, and kale. They have become increasingly popularFootnote 1 as they are highly nutritious, tender, and flavourfulFootnote 2. Also, they are often sold pre-washed and ready-to-eat.
Unfortunately, leafy baby vegetables have been associated with recallsFootnote 3, Footnote 4 and outbreaksFootnote 5 of foodborne illnesses as they can become contaminated with pathogens during production, harvest, post-harvest handling, packaging, distribution, and/or at retail. When consumed, the presence of bacterial pathogens creates the potential for foodborne illness.
When was the survey conducted
The survey was conducted over a 3-year period from April 1, 2018 to March 31, 2021.
Where were the samples collected from
Samples were collected from national retail chains and local/regional grocery stores located in the following 11 major cities across Canada:
- Halifax
- Moncton or Saint John
- Quebec City
- Montreal
- Toronto
- Ottawa
- Vancouver
- Victoria or Kelowna
- Calgary
- Saskatoon
- Winnipeg
The planned number of samples to be collected from each city was based on the population of the province in which the city was located relative to the total population of Canada.
How many and what kind of samples were collected
A total of 3172 pre-packaged baby leafy vegetable samples were collected. A sample consisted of a single or multiple consumer sized packages of the same lot weighing at least 250g.
What were the samples tested for
All samples were tested for L. monocytogenes, Salmonella spp., E. coli O157 and generic E. coli. L. monocytogenes, Salmonella spp. and E. coli O157 are pathogenic bacteria while generic E. coli is an indicator of the overall hygienic and sanitary conditions under which the samples have been produced, processed, stored and transported.
What methods were used to test the samples
Samples were analyzed using analytical methods published in Health Canada's Compendium of Analytical Methods for the Microbiological Analysis of FoodsFootnote 6 that were suitable for the testing of baby leafy vegetables.
How were the samples assessed
The samples were assessed using criteria based on the principles of Health Canada's Health Products and Food Branch Standards and Guidelines for Microbiological Safety of Foods – An Interpretive SummaryFootnote 7 and the Food and Drugs ActFootnote 8 (Section 4(1)).
| Bacteria | Satisfactory | Investigative | Unsatisfactory |
|---|---|---|---|
| Salmonella spp. | Not detected | Not applicable | Detected |
| L. monocytogenes | Not detected | Detected | Not applicable |
| E. coli O157 | Not detected | Not applicable | Detected |
| Generic E. coli | ≤ 102 MPN/g | 102 < × ≤ 103 MPN/g | >103 MPN/g |
No assessment guidelines had been established in Canada for the presence of Salmonella spp. or L. monocytogenes in fresh baby leafy vegetables at the time of writing this report. While both bacteria are pathogenic to humans, each have unique characteristics (for example, growth potential, infectious dose) which result in different levels of risk when present in baby leafy vegetables. Consequently, the presence of L. monocytogenes was assessed as investigative as it could be a violation of the Food and Drugs Act Section 4(1)aFootnote 8 whereas the presence of Salmonella spp. was assessed as unsatisfactory as it is considered a violation of the Food and Drugs Act Section 4(1)aFootnote 8.
What were the survey results
Over 99.5% of the samples tested were found to be satisfactory. Salmonella spp., and E. coli O157 were not found in any of the 3172 samples tested. L. monocytogenes was found in 12/3172 (0.38%) samples at levels ranging from <5 to 360 CFU/g. Generic E. coli at elevated levels (102 < × ≤ 103 MPN/g) were found in 3/3172 (0.09%) samples.
| Bacterial analysis | Number of samples tested | Satisfactory (%) | Investigative (%) | Unsatisfactory |
|---|---|---|---|---|
| Salmonella spp. | 3172 | 3157 | Not applicable | 0 |
| E. coli O157 | Not applicable | 0 | ||
| L. monocytogenes | 12 (0.38) | Not applicable | ||
| Generic E. coli | 3 (0.09) | 0 | ||
| Total | 3172 | 3157 (99.5) | 15 (0.47) | 0 |
Survey results are also presented by production practice (table 3), origin (table 4) and product type (table 5).
| Production practice | Number of samples tested (%) | Satisfactory | Investigative |
|---|---|---|---|
| Conventional | 2259 (71.2) | 2244 | 15 |
| Organic | 913 (28.8) | 913 | 0 |
| Total | 3172 | 3157 | 15 |
| Product origin | Number of samples tested (%) | Satisfactory | Investigative |
|---|---|---|---|
| Domestic | 473 (14.9) | 469 | 4 |
| Import | 2513 (79.2) | 2506 | 7 |
| Domestic and import | 179 (5.6) | 176 | 3 |
| Unknown Table Note a | 7 (0.2) | 6 | 1 |
| Total | 3172 | 3157 | 15 |
Table Note
- Table note a
-
Unknown refers to those samples for which the country of origin could not be assigned from the product label or available sample information.
| Product type | Number of samples tested (%) | Satisfactory | Investigative |
|---|---|---|---|
| Mixed baby greens | 1343 (42.3) | 1339 | 4 |
| Baby spinach | 1186 (37.4) | 1179 | 7 |
| Baby arugula | 499 (15.7) | 496 | 3 |
| Baby kale | 143 (4.5) | 142 | 1 |
| Baby bok choi | 1 (0.03) | 1 | 0 |
| Total | 3172 | 3157 | 15 |
What do the survey results mean
Previous Canadian and international studiesFootnote 9, Footnote 10, Footnote 11, Footnote 12 on the microbial quality and safety of retail fresh baby leafy vegetables have shown results approximating those in our study. Differing prevalence rates between studies may be attributable to differences in product types tested, methodology, study design, etc.
Overall, our survey results indicate that baby leafy vegetables sold in Canada are generally safe for consumption, however they can occasionally be contaminated. Consequently, as with all foods, and especially with those that are consumed raw, good hygienic practices are recommended for producers, retailers and consumers.
What is done with the survey results
All results are used to:
- inform risk management decisions
- support program design and re-design
While no illness were related to the investigative and unsatisfactory samples, these results triggered appropriate follow-up actions. Follow-up actions may have included:
- facility inspections
- additional sampling and testing
- removal of affected products from the marketplace
Can I access the survey data
Yes. The data will be accessible on the Open Government Portal.
References
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