Monitoring VTEC in Food
In addition to the surveillance systems designed to monitor human health, Canada has as national food safety system that is designed to protect the health of consumers and ensure fair practices in the food industry according to the principles recommended by the Codex Alimentarious (CAC, 2013). Within this system, food monitoring programs are used to (i) provide information on specific hazards in foods, (ii) contribute to the development of risk management options, and (iii) support system-wide review activities.
Food monitoring programs contribute to hazard identification and provide data to inform quantification of exposure. Monitoring may be conducted to support compliance verification, standard development and to demonstrate country equivalency as well as to assess the effectiveness of implemented risk management measures during monitoring and system review. A limitation of microbial food surveillance data is that the foodborne pathogens may be present at very low frequency in foods. Thus, unless very large numbers of samples from a population are tested, it may be difficult to assess the prevalence of these pathogens with a high degree of certainty.
Federal VTEC Monitoring/Testing Programs
National Microbiological Monitoring Program and Food Safety Oversight Program
The CFIA conducts two monitoring programs which include testing foods for VTEC, these are the National Microbiological Monitoring Program (NMMP) and the Food Safety Oversight (FSO) Program. The NMMP is primarily focused on federally registered production facilities and is dependent upon inspector sampling at registered establishments. In the FSO Program, which was recently introduced to complement the NMMP, samples are collected by both CFIA inspectors and third-party samplers at registered establishments and at retail stores. Results from both programs are published annually on the CFIA website (CFIA Testing).
Targeted Surveys Program
The CFIA also performs Targeted Surveys to examine hazards and/or foods that are not routinely included in other CFIA monitoring programs. Unlike NMMP and FSO, which monitor established food hazard combinations over time, the foods included in Targeted Surveys may vary from year to year. From April 1, 2013 to March 31, 2018, six types of foods were sampled and tested for VTEC (Table 7): fresh and fresh-cut RTE fruit and vegetables, raw milk cheeses, raw ground pork, beef and veal, nuts and nut butters, dried sprouted seeds and cold-pressed/ unpasteurized juices and ciders (Table 7).
As discussed in FoodNet Canada, FoodNet Canada provides integrated human, food, and environmental monitoring within designated “sentinel sites”. Sampling of ground beef at retail is a core activity under FoodNet Canada and is included every year. Depending on public health concerns identified by partners, additional sampling of other targeted products is conducted. In recent years, targeted sampling has included ground pork, veal or pork sausage. FoodNet Canada presents their surveillance data through their annual reports (NESP Reports).
Results of Federal VTEC Monitoring/Testing Programs in Food
Raw Ground Beef, Pork and Veal and Precursor Materials
Under the NMMP, finished raw ground beef or veal products (FRGBP) and precursor materials are tested for E. coli O157:H7/NM. Sampling of FRGBP is performed at the first grinding phase (coarse grind) of trims and other precursor materials of selected productions lots of a minimum 900 kg. Precursor materials intended for use in FRGBP included trims, boneless beef, coarse ground beef, hearts, head meat, cheek meat, tongue roots, weasand meat, and chucks. The frequency of sampling at domestic establishments is based on the size of the establishment and its compliance history. Sampling frequency is higher in the summer. From April 1, 2013 to March 31, 2018, E. coli O157:H7/NM was isolated from 0.09% (n = 3,273) of domestic FRGBP samples and in 0.13% (n = 3,885) domestic samples of FRGBP precursor (Table 7).
FoodNet testing of retail ground beef over 4 years (2014 to 2017) had a VTEC isolation rate of 2.0% (n = 1458). The frequency of VTEC in retail ground pork was 6.1% (n = 98) in 2014 and 2015. A similar frequency of VTEC 6.3% (n = 334) was reported for retail veal in 2017 (Table 6).
Under the NMMP, ready-to-eat (RTE) meats, that have not been fully cooked, such as some dry, semi-dry or fermented products, are tested for E. coli O157:H7/NM. No VTEC were isolated from 22 domestic RTE meat samples and 15 imported RTE meat samples tested under the NMMP from April 1, 2013 to March 31, 2018 (Table 7).
Raw Milk Cheeses
Under the NMMP, raw milk cheeses, including cow, goat and sheep’s milk cheeses, were tested for E. coli O157:H7/NM. No VTEC were isolated from 247 domestic raw milk cheese samples and 550 imported raw milk cheese samples tested under the NMMP from April 1, 2013 to March 31, 2018 (Table 7).
Under the NMMP and FSO, fresh and fresh-cut RTE fruits and vegetables are tested for VTEC. Fresh fruits and vegetables include imported whole, fresh leafy vegetables, tomatoes, fresh herbs, green onions, peppers, sprouted seeds and beans, cantaloupes, papayas, mangoes and berries. Fresh-cut RTE fruits and vegetables are defined as fresh fruits or vegetables that were washed and further minimally processed (e.g., peeled, cored and sliced, chopped and/or shredded) prior to being packaged. Also included are pre-packaged salads. Testing is currently for E. coli O157:H7/NM, although some fresh produce was tested for non-O157 VTEC in the past. No E. coli O157:H7/NM were isolated from 2617 domestic fresh and fresh-cut RTE fruits and vegetable samples and 4882 imported fresh and fresh-cut RTE fruits and vegetable samples tested under the NMMP and FSO from April 1, 2013 to March 31, 2018 (Table 7). No E. coli O157:H7/NM or non-O157 VTEC were isolated from 66 domestic fresh and fresh-cut RTE fruits and vegetable samples and 187 imported fresh and fresh-cut RTE fruits and vegetable samples tested under the NMMP from April 1, 2013 to March 31, 2018 (Table 7).
Under Targeted Surveys, fresh and fresh-cut RTE fruit and vegetable products tested included fresh herbs, leafy vegetables, green onions, cucumbers, sprouted seeds and beans, mangos, papayas, and stone fruits (peach, plum, nectarine, apricot, etc.). Fresh-cut RTE fruits and vegetables included pre-packaged RTE vegetables and fruits (e.g., berries, mangos, pineapple), including melons (e.g., watermelon, honeydew melon, and cantaloupe). No E. coli O157:H7/NM where isolated from 28,715 domestic and imported fresh and fresh-cut RTE fruits and vegetable samples tested for E. coli O157:H7/NM under the Targeted Surveys from April 1, 2013 to March 31, 2018 (Table 7). Six non-O157 VTEC were isolated from 1251 domestic and imported fresh and fresh-cut RTE fruits and vegetable samples tested for E. coli O157:H7/NM and non-O157 VTEC under the Targeted Surveys during the same time period (Table 7).
Other Plant-Based Foods
In addition to the foods listed above, Targeted Surveys were performed on nuts and nut butters, dried sprouted seeds and cold-pressed/ unpasteurized juice and cider samples between April 1, 2013 and March 31, 2018 (Table 7). No VTEC were isolated from 3,972 domestic and imported nut and nut butter samples tested for E. coli O157:H7/NM. No VTEC were isolated from 322 domestic and imported dried sprouted seeds tested for E. coli O157:H7/NM but 0.4% (n = 1,028) domestic and imported dried sprouted seeds tested for E. coli O157:H7/NM and non-O157 VTEC were found to contain non-O157 E. coli. Lastly, no VTEC were isolated from 1,133 domestic and imported cold-pressed/ unpasteurized juice and cider samples tested for E. coli O157:H7/NM.
Industry VTEC Monitoring/Testing
Abattoirs producing raw beef trimmings for export to the USA participate in a CFIA-designed verification sampling program. Participation in this program is mandatory for abattoirs to maintain their eligibility to export to the USA. Samples are collected by the operators under the supervision of the CFIA veterinarian in charge and are submitted to private laboratories for analysis for the presence of LEE-positive VTEC belonging to the serogroups O26, O45, O103, O111, O121, and O145.
The private laboratories are required to use only test methods that have been granted a No Objection Letter (NOL) from the United States Department of Agriculture (USDA) Food Safety Inspection Services (FSIS) for the screening for the presence of the targeted VTEC. All results obtained under this program, i.e., negative, presumptive positive and culturally confirmed positives, are reported by the operator's contracted laboratory to the CFIA.
This program complements E. coli O157:H7/NM testing that is performed by the CFIA under its NMMP, as sampling frequencies for both industry and CFIA testing are the same and the same robust N60 sampling approach is used for both.
Surveillance data for VTEC in foods is collected through the CFIA National Microbiological Monitoring Program and Food Safety Oversight Program, which are supplemented by Targeted Surveys of selected products. Data on VTEC contamination of retail ground beef, pork and veal is collected through FoodNet Canada. The primary findings of these surveys are as follows:
- Foods for which surveillance data is available include; raw ground beef, pork, and veal, ground meat precursor materials, ready-to-eat meats, raw milk cheeses, fresh produce, nuts and nut butter, dried sprouts, cold-pressed/unpasteurised apple juice. Both domestic and imported products have been surveyed. VTEC were isolated from raw ground meats, fresh produce and dried sprouts, but not other foods tested.
- Domestic raw ground beef and veal was positive for VTEC O157 at a prevalence of 0.09% (n = 3,273) for 325 g samples.
- Domestic raw ground beef precursor was positive for VTEC O157 at a prevalence of 0.13% (n = 3,885) for 325 g samples.
- VTEC isolation rate from retail ground beef 2.0% (n = 1458), retail ground pork 6.1% (n = 98) and 6.3% (n = 334) for 25 g samples.
- A total of 36,214 samples of fresh and fresh cut ready-to eat vegetables (25 g or 125 g) of domestic or imported origin was tested for VTEC O157 and was found negative. Non-O157 VTEC was isolated at a rate of 0.40% (1,504).
- The prevalence of non-O157 VTEC in dried sprouts was 0.39% (n = 1,028) for 25 g samples.
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