Bacterial Pathogens and Indicators in Imported Romaine Lettuce - April 1, 2019, to March 31, 2024

The survey was conducted to provide enhanced oversight of imported romaine lettuce sold at retail in Canada. Romaine lettuce is popular among Canadians^{Footnote 2} as part of a healthy diet including plenty of fruits and vegetables. Unfortunately, leafy green vegetables (including romaine lettuce) have been associated with foodborne illness outbreaks of bacterial pathogens such as E. coli O157:H7, and Salmonella spp.^{Footnote 3Footnote 4}. Between 2017 and 2020, romaine lettuce imported from the United States (US) were associated with several foodborne illness outbreaks of E. coli O157:H7 in the US^{Footnote 5Footnote 6Footnote 7Footnote 8}, and Canada^{Footnote 9Footnote 10Footnote 11}. This survey was initiated in response to these reoccurring outbreaks. Additionally, the CFIA implemented import requirements for products containing romaine lettuce harvested from the affected US growing regions^{Footnote 12Footnote 13}.

Food safety investigations, and traceback studies into the outbreaks revealed that the contamination was associated with the close proximity of the lettuce growing fields to concentrated animal feeding operations^{Footnote 14Footnote 15}. Lettuce in growing fields could have been contaminated with E. coli O157:H7 from cattle feces via irrigation water, wind and other means^{Footnote 14Footnote 15}. Food safety action plans and control measures were implemented in the implicated US growing regions in 2020^{Footnote 16}.

The survey was conducted over a 5-year period from April 1, 2019, to March 31, 2024.

Samples were collected from national retail chains and local/regional grocery stores located in the following 11 major cities across Canada:

• Halifax
• Moncton
• Quebec City
• Montreal
• Toronto
• Ottawa
• Vancouver
• Victoria
• 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.

A total of 4450 imported fresh romaine lettuce samples including whole (1258), hearts (1822), and fresh-cut romaine or romaine lettuce-based salads (1370) were collected over the 5-year survey period. A sample consisted of a single or multiple consumer sized packages of the same lot weighing at least 250 g.

The imported fresh romaine lettuce samples (whole, hearts, and fresh-cut or salads) were tested for the presence of E. coli O157:H7/NM, Salmonella spp., and generic E. coli (table 1). E. coli O157:H7/NM, and Salmonella spp. 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.

Samples were analyzed using analytical methods published in Health Canada's Compendium of Analytical Methods for the Microbiological Analysis of Foods^{Footnote 17} that were suitable for the testing of romaine lettuce.

The samples were assessed using criteria based on the principles of the following Health Canada documents: Health Products and Food Branch (HPFB) Standards and Guidelines for Microbiological Safety of Foods – An Interpretive Summary^{Footnote 18}, and the Food and Drugs Act (Section 4(1)a)^{Footnote 19}. See table 2.

At the time of writing this report, no assessment guidelines had been established in Canada for the presence of Salmonella spp. in fresh vegetables. As Salmonella spp. is considered pathogenic to humans, its presence was assessed as unsatisfactory and might be considered a violation of the Food and Drugs Act Section 4(1)a^{Footnote 19}.

Almost all (99.98%) of the samples tested were found to be satisfactory. E. coli O157:H7/NM and Salmonella spp. were not found in any of the (0/4432) and (0/2795) samples, respectively. Generic E. coli at elevated levels was found in one of the 4450 samples (table 3).

Survey samples are also presented by product type (table 4), by fresh-cut romaine lettuce or romaine lettuce-based salad product sub-types (table 5), origin (table 6), and production practice (table 7).

The majority of the romaine lettuce samples were imported from the US (92.1%) with the remainder from Mexico (6.9%), and other countries (1%) (table 6).

Most of the romaine lettuce samples tested in this survey were conventionally produced (81.9%) (table 7).

The result of the current study has shown results approximating those from a previous Canadian study^{Footnote 20} on the microbial quality, and safety of leafy vegetables including imported romaine lettuce (whole and fresh-cut).

This 5-year survey was one of several collaborative actions of Canadian food safety authorities in response to the reoccurring E. coli O157:H7 outbreaks in the period 2017 to 2020^{Footnote 12Footnote 13} to verify the safety of produce available to Canadians.

Overall, our survey results indicate that imported romaine lettuce products (whole, hearts and fresh-cut or salads) sold in Canada are generally safe for consumption. However, as with all foods, and especially those that are RTE, good hygienic practices are recommended for producers, retailers, and consumers.

All results are used to:

• inform risk management decisions
• support program design and re-design

The investigative sample triggered appropriate follow-up activities, as necessary.

The data will be accessible on the Open Government Portal.