Preventive controls for E. coli O157/NM in raw beef products
On this page
- Control measures
- Actions when products test positive for E. coli O157
- Sampling and testing program
- Process awareness program to detect trends
- High event period (HEP)
- Appendix: Validation of pathogen reduction step(s)
The purpose of this document is to provide information on measures to control E. coli O157 in raw beef products.
According to Health Canada's Guidance Document on E. coli O157:H7 and E. coli O157:NM in Raw Beef, E. coli O157 contamination of raw beef is a hazard likely to occur, and the use of any meat components derived from a contaminated carcass to make finished raw ground beef products (FRGBP) or beef product processed for raw consumption (BPPRC) is considered a risk to human health. Therefore, in order to meet section 47 of the Safe Food for Canadians Regulations (SFCR), licence holders who manufacture, process, treat or package precursor material (PM) or BPPRC must address this hazard and demonstrate that they have control measures in place that are effective in achieving non detectable levels of E. coli O157 in their final products.
In addition, the document Preventive control requirements for biological hazards in meat products / control measures for E. coli O157 in raw beef products, incorporated by reference in section 47 of the SFCR, specifically requires licence holders who manufacture, process, treat or package PM or BPPRC to have a sampling and testing program and a process awareness program, with defined High Event Period and notification procedures, for the presence of E. coli O157 in their products.
Note that many useful definitions can be found in the document Preventive control requirements for biological hazards in meat products / Control measures for E. coli O157 in raw beef products as well as in Health Canada's Guidance Document on E. coli O157:H7 and E. coli O157:NM in Raw Beef.
1. Beef slaughter operations
In beef slaughter operations, control measures for E. coli O157 include:
- Dressing procedures that prevent the contamination of carcasses and other raw meat products with biological hazards,
- At least one pathogen reduction intervention on carcasses, for example steam/hot water pasteurization, organic acid sprays, etc. (refer to the end of this document for specific guidance on validation of pathogen reduction step(s))
- Conditions to prevent airborne contamination of carcasses,
- Trained personnel who follow Good Hygiene and Manufacturing Practices to prevent the contamination of carcasses during handling,
- Conditions to prevent the contamination of carcasses during storage and transportation.
For additional control, beef slaughter facilities may also choose to:
- Collaborate with producers and transporters on pre-harvest management practices aimed at reducing E. coli O157 load in live animals presented for slaughter,
- Assess the cleanliness of live animals (e.g., mud scoring) at receiving and use this information to establish better procedures to control biological hazards such as, implementing appropriate sequencing of the affected lot or animals during slaughter, implementing reduced line speeds, adding more trimmers on the production line and /or enhancing the monitoring of control measures designed to reduce the hazard to below detectable levels,
- Use a hide-on carcass wash to remove excess organic matter and reduce airborne particles,
- Apply any other additional intervention steps, as part of a multi-hurdle approach, contributing to the reduction of E. coli O157 contamination of raw meat product to below detectable level.
2. Beef processing operations
In facilities processing raw beef products (boning, cutting, grinding), control measures for E. coli O157 include:
- Conditions during storage prior to processing that prevent the contamination of the carcasses,
- Trained personnel who follow Good Hygiene and Manufacturing Practices to prevent the contamination of carcasses/raw meat products during handling,
In addition, it is important to have the following control measures, as applicable to the situation:
Suppliers of precursor material
The document Preventive control requirements for biological hazards in meat products / control measures for E. coli O157 in raw beef products requires facilities that supply precursor materials to other facilities that may produce FRGBP or BPPRC to have a sampling and testing program and a process awareness program to make sure that all lots that are shipped have no detectable amount of E. coli O157.
Purchase specification agreement
It is important that facilities supplying PM and facilities receiving PM to make FRGBP or BPPRC establish purchase specification agreements that include as a minimum the following controls:
- The operator of the supplying facility identifies in a Letter of Guarantee (LOG) the validated intervention(s) (including CCPs) as well as other measures used to reduce, prevent or eliminate the hazard associated with E. coli O157 for all their beef products.
- The supplier has a written program to verify and monitor that only products that tested "not detected" are supplied for the production of FRGBP. For example, the shipped product could be accompanied with test results for each lot of PM, or an agreement could be made between the supplier and receiver to identify lot(s) that tested "not detected" with appropriate labels or identification marks for verification purposes.
- In situations where receiving facilities choose to perform verification testing of PM, or where supplying facilities ship product pending test result(s), the supplying and receiving facilities should have a prior agreement as to whether a presumptive positive is accepted as a positive result or if a cultural confirmation will be pursued to determine either a confirmed positive or a negative result.
Facilities making FRGBP or BPPRC
Facilities that receive PM to make FRGBP or BPPRC have controls in place to make sure that only PM that tested "not detected" is used in the production of FRGBP or BPPRC. This includes having a purchase specification agreement with their supplier as described in the previous bullet.
Raw beef not used in the production of FRGBP or BPPRC
- Primal and sub-primal cuts that will be sold to the consumer as is or cut into smaller cuts like steaks, cube steaks and roasts, including those cuts that have been mechanically tenderized, do not pose the same level of risk as FRGBP or BPPRC. Customary cooking of these products is expected to inactivate any E. coli O157 that might be present on the surface. Therefore, it is not necessary for a facility producing and distributing pre-packaged primal and sub-primal cuts, to test these products for E. coli O157, provided that control measures are in place to prevent these products from entering the production of FRGBP and BPPRC.
- Precursor materials that will be further processed into a RTE product by a processing facility also do not pose the same level of risk as FRGBP or BPPRC. The full lethality treatment to render the product RTE will inactivate any E. coli O157 that may be present throughout in the product. Therefore, it is not necessary for facilities producing precursor materials for cooking to test these products for E. coli O157, provided that control measures are in place to make sure that the untested precursor material will not be used for making FRGBP and BPPRC. These control measures include:
- cautionary labelling on the product (for example "untested - for cooking only"),
- proper segregation procedures from other PM that will not be subjected to a lethality treatment,
- use of company seals during transportation,
- guarantee with the receiving facility that the product will be cooked.
Sampling and testing program
Establishments that are handling PM (raw beef that could be used to make FRGBP or BPPRC) must have a sampling program to test for the presence of E. coli O157 in every lot of PM produced.
Precursor materials (PM) include:
- beef trim (beef manufacturing trims produced in slaughter facilities)
- bench trim (beef trimmings produced in facilities that do not have on-site slaughter but perform further beef processing activities)
- head meat
- cheek meat
- tongue roots
- weasand meat
- comminuted beef products (for example; coarse ground beef, finely textured meat (FTM))
- other raw beef components such as primal or sub-primal cuts (for example; chucks, top round, sirloin cuts)
Establishments producing BPPRC could use untested PM if they implement a sampling program to test for the presence of E. coli O157 in every lot of BPPRC produced.
Note that it is not required to sample and test the following products:
- Primal and subprimal cuts that will be sold to the consumer as is, or cut into smaller cuts like steaks, cube steaks and roasts (but not ground), including those cuts that have been mechanically tenderized, provided that control measures are in place to prevent these products from entering the production of FRGBP and BPPRC.
- Trimmings that will be further processed into RTE products by a federally licensed operator, provided that the process includes a full lethality treatment.
2. Sampling procedures
As per definitionFootnote 1, a lot cannot consist of more than one type of precursor material and cannot weigh more than 4,500 kg (approximately), which is equivalent to a maximum of five combos (considering that a combo weighs around 900Kg).
An alternate unit to a combo may be defined and used by the operator (e.g., a pallet of boxes or a tote, buggy, vat, tub, etc.), provided the weight of the lot does not exceed approximately 4,500 kg.
In the case of small operators, a lot could consist of more than one day of production (and up to five consecutive calendar days) provided that the weight of the lot does not exceed 4,500 kg; note that full sanitation and cleaning at the end of each production day would still be needed to meet hygiene requirements.
For precursor material amenable to excision sampling (e.g., beef trim, bench trim, head meat, cheek meat, tongue roots, weasand meat, hearts, primal or sub-primal cuts), a minimum of 60 sub-samples of 5 to 6 g each adding to a total of 325 g must be examined per lot.
All combos/units must be equally represented in the sample. For example, 12 individual pieces would be taken from each combo of a five combo lot. For alternate units, a minimum of 60 equally distributed pieces must be collected across the lot (e.g., a 10 vat lot of trim could be sampled by collecting six pieces per vat, a five pallet lot could be sampled by collecting 12 pieces per pallet, etc.).
The material collected for testing should represent the outside surface of the product (e.g., carcass surface for sampled trim, exposed surfaces of the heart muscle, external aspect of the diaphragm muscle, etc.). In other words, it must not be taken from inner meat tissue unless the normal production process has left only inner tissue to sample.
For PM not amenable to excision sampling (e.g., finely textured beef), a minimum of five sample units of approximately 65 g each must be collected from the lot. Sample units must be representative of the whole lot.
Alternate sampling procedures may be used provided that they are at least as robust as the ones described in this document and that they have been validated.
3. Testing considerations for E. coli O157
Note that the integrity of the lot should be maintained pending laboratory test results ("hold and test") to prevent a recall situation.
It is important that all testing, with both screening and confirmation methodologies, is done using approved methods (which can be obtained from the Health Canada Compendium of Analytical Methods) and performed in a laboratory accredited by the Standards Council of Canada (SCC), the Canadian Association for Laboratory Accreditation (CALA), or another accreditation bodyFootnote 2.
The samples collected as per the sampling procedures described above may be tested as a composite of 325 ± 32.5 g, unless otherwise specified in the test method used.
A sample that tested positive with a screening method (also called a "presumptive positive") will be considered positive (contaminated with E. coli O157) unless proven otherwise by confirmatory testing.
Additional requirements may apply when testing product for export to other countries, such as the United States of America.
Actions when products test positive for E. coli O157
The document Preventive control requirements for biological hazards in meat products / control measures for E. coli O157 in raw beef products requires operators to inform the CFIA of any positive results for E. coli O157 (presumptive or confirmed). In situations where an operator decides to send a presumptive positive product for confirmatory testing, final results should also be made available to CFIA (whether confirmed "positive" or "not detected").
Upon receipt of a positive result for E. coli O157 (whether presumptive or confirmed positive), an operator will determine the scope of implicated product as follows:
- PM: The lot of PM that tested positive and any lot of PM, FRGBP or of a prepared meat product that contains a portion of the PM from the lot that tested positive will be considered implicated. Additionally, operators should consider whether any other products or lots should be designated as suspect products or lots based on factors such as the source of PM, time of production, production line and high event period.
- FRGBP: The lot of FRGBP that tested positive will be considered implicated. Any lot of FRGBP or of a further processed product that contains a portion of the lot that tested positive will be considered implicated.
The scope of implicated products described in this section may be further expanded depending on the following indications in the overall context of the situation:
- Epidemiological evidence (data, descriptive or analytical in nature, demonstrating an association between a food product and human illness as determined by the study of the frequency, distribution and determinants of the particular outbreak);
- High Event Period (HEP) situation;
- Out-of-control process; and
- Inadequate lot identification and sampling protocols.
Intact raw beef products linked to the same source material as PM that has tested positive, may be implicated, on a case-by-case basis, depending on their end use (e.g., FRGBP, mechanically tenderized beef or BPPRC), when there is epidemiological evidence of illness, process deviations, or HEP situation.
3. Product disposition
The following are options available to operators for the controlled disposition of implicated or suspect products.
Cooking can be performed to salvage the product by further processing into a fully cooked finished product through a cooking process validated as equivalent to a full lethality treatment for E. coli O157. A beef product is considered to have received a full lethality treatment for E. coli O157 when the manufacturing process has been scientifically validated to achieve a five log reduction of E. coli O157.
Denature and condemnation
Operators have the option to denature and condemn implicated or suspect product with the use of suitable denaturing agents.
Rejection of positive products
In the case of a product received from another licensed operator, the operator may reject the product and, provided the supplier has agreed in advance, return the product to the supplier under company seal for appropriate disposition. It is important that both operators keep records to ensure that the positive product is adequately controlled until it is subjected to either one of the two disposition options described above.
4. Follow up sampling to a positive found in FRGBP
When a positive E. coli O157 result is obtained under a verification sampling plan of FRGBP (whether from CFIA M201 or industry's own verification program), it is important that operators conduct follow up sampling and testing to confirm that their corrective actions were effective. To do so, the sampling frequencies and actions described below should be followed:
|Production volume (kg/yr)
|Total number of follow-up samples
|25,000 - 400,000
|400,000 - 40,000,000
- Table Note 3
Using a maximum of two follow-up samples per shift per day and a minimum of three follow-up samples per week.
The operator will randomly select a lot and collect five sample units of 200 g each in a sanitary manner.
If there is a positive sample during the follow up testing, the operator will continue sampling until 8, 12 or 16 consecutive samples that test "not detected" have been collected (as per Table 1, above).
Product should be held pending test results when follow-up testing is conducted to prevent a recall situation.
Process awareness program to detect trends
The objective of process awareness is to identify trends of events over time which may indicate potential loss of process control. Process awareness may include actions or measures taken to control incoming material, time and temperature controls, physical, chemical and microbiological controls etc. The document Preventive control requirements for biological hazards in meat products / control measures for E. coli O157 in raw beef products requires operators that produce PM or BPPRC to develop and implement a process awareness program to monitor for the presence of E. coli O157 and determine trends over time. As a part of process awareness, criteria/limits are established to define periods when the analysis indicates a potential loss of control. Out of control situations or deviations determined through process awareness should be addressed through root cause analysis and appropriate corrective actions.
Process awareness can be enhanced through routine recording of the chronology or specific times of certain operations, such as slaughter, fabrication, trim collection and grinding. This information can enable real-time or retroactive determination of relationships between source materials and between products, which can help in assessing the significance of positive test results.
2. Process awareness for establishments producing PM
It is recommended that operators that produce PM (slaughter/further processing/grinding establishments) also monitor trends of generic E. coli or other indicator organisms in addition to E. coli O157 as part of their process awareness program. To be meaningful, a process awareness program should take into account all results obtained for PM, whether from CFIA testing, operator's testing or third party testing.
3. Process awareness for establishments producing FRGBP
Operators that produce FRGBP should test their products for an indicator organism such as generic E. coli to monitor trends of contamination and verify control of the process. The operator will determine their sampling frequency based on their specific operation and production volume. The following annual sampling frequencies are recommended as a minimum:
|Production volume (kg/yr)
|Minimum number of samples/year Table Note 4
|25,000 - 400,000
|400,000 - 40,000,000
- Table Note 4
Samples to be evenly distributed throughout the year.
4. Follow-up actions when process awareness indicates a loss of control
The document Preventive control requirements for biological hazards in meat products / control measures for E. coli O157 in raw beef products requires operators to notify CFIA inspection staff when there is an indication of a potential loss of control, to perform root cause analysis and to take appropriate corrective actions and preventative measures according to their written program. Even if no root cause can be identified, a report indicating this fact and a rationale for this conclusion should be made available to the CFIA.
High event period (HEP)
The document Preventive control requirements for biological hazards in meat products / control measures for E. coli O157 in raw beef products requires beef establishments producing more than seven lots of PM per day (i.e., beef slaughter and processing establishments) to identify and document HEP criteria as part of their process awareness program.
A HEP is a situation when an operator receives a high number or rate of positive results for E. coli O157 in samples of precursor materials taken from production lots containing the same source material. PM that were produced from one or more carcasses slaughtered and dressed consecutively or intermittently within a defined period of time (e.g., shift) are considered to be from the same source material.
A HEP may indicate systemic breakdown of the slaughter dressing operation that may implicate other parts of the beef carcass in addition to the PM that tested positive. It may indicate an unsanitary condition during the slaughter/dressing operation which may have resulted in widespread contamination across production lots. As such, the PM that tested "not detected" but obtained from same source materials as those which have tested positive may be considered as suspect PM.
HEP will allow for adequate identification of implicated and suspect products beyond the products that were reported positive.
For example, the demonstration of a temporal and spatial relationship between positive lots could indicate a potential loss of control over the process and a likely HEP situation. Here temporal means the time of processing based on recorded start and stop times of relevant operations and spatial refers to the area of carcass from which different types of trim and intact cuts are derived. Demonstrating a temporal and spatial relationship between positive and other lots could be used to determine the scope of implicated products.
Based on the investigation, operators identify whether the HEP situation is localized or systemic and, accordingly, determine the scope of implicated product(s). A localized situation may affect only a short production time or a specific product(s) due to an isolated problem while a systemic situation may affect products over a greater period of time or more products due to a broader problem.
2. High event period (HEP) numerical criteria
The following table is provided to help operators develop numerical criteria to determine whether they have experienced a HEP. The table provides numbers of positive results (the first column) occurring within a specified number of samples (entries in the remaining columns), that would indicate that the percent positive of E. coli O157 findings would be statistically significantly greater than or equal to 5%, at the following percent confidence intervals:
- 95% confidence;
- close to 98.85% confidence; and
- close to 99.95%.
|Number of positive lots Table Note 6
|Total number of lots required to be tested at different confidence intervals
|Total number of lots required to be tested at different confidence intervals
|Total number of lots required to be tested at different confidence intervals
- Table Note 5
Acknowledgement: The statistical confidence intervals presented in Table 3 have been excerpted from the United States Department of Agriculture - Food Safety Inspection Service (FSIS) Compliance Guideline for Establishments Sampling Beef Trimmings for Shiga Toxin-Producing Escherichia coli (STEC) Organisms or Virulence Markers
- Table Note 6
The test result from one composite sample is considered one positive or "not detected" result.
If there were four or more positive results within 28 samples, then there would be 95% confidence that the process positive percent was not less than 5%. If there were four or more positive results within 18 samples, then there would be 98.85% confidence that the process positive percent was not less than 5%. If there were four or more positive results within eight samples, then there is 99.95% confidence that the positive percent was not less than 5%.
At a lower confidence level, an HEP will get detected at a lower observed positive rate and the chance of releasing an adulterated product into commerce is minimized. For example:
- At 95% confidence level, an HEP will get detected when five out of 40 lots test positive.
- At 98.85% confidence level, an HEP will get detected when six out of 38 lots test positive.
- At 99.95% confidence level, an HEP will get detected when eight out of 38 lots test positive.
Operators may wish to choose more stringent criteria, for example, an operator may decide to declare an HEP if the percent positive exceeds 3.5%.
3. Follow up actions in HEP situations
The document Preventive control requirements for biological hazards in meat products / control measures for E. coli O157 in raw beef products, requires operators to notify CFIA inspection staff when they experience a HEP. Operators will investigate and determine whether the lots of PM that tested "not detected", as well as the untested intact primal and sub-primal products produced from the same source material as the contaminated PM, have E. coli O157 below detectable level. The results of this investigation must be provided to the CFIA.
During a HEP situation, primal and sub-primal cuts linked in time and space to positive lots of PM may be considered contaminated because they were prepared under unsanitary conditions. Some of the factors considered in this determination will be:
- rate of PM E. coli O157 positives during the HEP;
- magnitude of process deviations during the HEP;
- microbial test results on primal and sub-primal cuts, if applicable, and other relevant test results;
- interventions, for example: antimicrobials applied to primal and sub-primal cuts;
- cross contamination controls; and
- end use of primal and sub-primal cuts.
Suspect primal and sub-primal cuts and other intact raw beef with or without antimicrobial application subjected to a robust sampling and testing procedure and that receive a negative test result for E. coli O157 may be distributed.
The actions taken in response to a HEP situation will depend upon the findings of the investigation of the positive results. As a follow-up action, the operator may consider increased testing after experiencing HEP, however if the establishment is able to find the root cause of HEP and takes corrective actions to prevent positive results from recurring, then an increase in testing would not be required. This increase in testing can be achieved by either defining smaller lots of trimmings (one combo bin instead of five combo bins) or selecting additional samples from five combo lots (e.g., N-75 instead of N-60) and should continue until the establishment has a high degree of confidence that the corrective actions are effective. Additionally, operator may increase monitoring and verification of both slaughter and dressing procedures, implement additional antimicrobial interventions and test additional products.
Appendix: Validation of pathogen reduction step(s)
Under the SFCR, control measures must be shown by evidence to be effective. This means that in-plant pathogen reduction step(s) must be validated and this validation must be documented in the PCP. General guidance on validation is provided in Evidence showing a control measure is effective. This appendix provides more specific details and guidance to help the beef processing industry validate their reduction step(s) for the pathogen E. coli O157.
The operator needs to determine and clearly identify in its PCP the intervention or the series of interventions that will be resulting in the reduction of E. coli O157 contamination to below detectable level and determine which one(s) will need to be validated accordingly. As appropriate, the operator should ensure that all chemicals used for antimicrobial interventions are used in accordance with Health Canada's assent.
Step 1: Gather scientific support documentation
The first step is to gather published scientific or technical information and literature indicating effectiveness of the intervention against E. coli O157. To the extent possible, the literature should also prove effectiveness of the intervention against indicator organisms. The scientific documentation should also provide relevant information with respect to critical operational parameters that need to be adhered to in order to achieve the desired food safety outcome.
Examples of critical operational parameters that may apply for the validation of a particular antimicrobial intervention include: pressure, temperature, time, chemical concentration, pH, contact time, carcass coverage by the product, spatial configuration, equipment design, settings or calibration, dwell time, water activity during drying and log reduction of targeted microorganisms.
Validation documentation gathered in another establishment can form the basis for completion of the first step of the validation process provided all the critical operating parameters are the same in both plants. Note, however, that this does not exempt from completing the subsequent step(s) necessary for validation of the selected intervention(s).
Step 2: On-site validation of the pathogen reduction step
The operator must demonstrate that the intervention is effective under the establishment operating conditions. This particular step is important because often laboratory conditions described in the literature are highly controlled as compared to the actual conditions in the establishment. The data should be gathered within the initial 120 days of implementing the new intervention or series of interventions to demonstrate that pathogen reduction capability is effectively achieved. The data becomes part of the documentation in support of validation.
a. Critical Operational Parameters
The operator must first identify all the relevant critical operational parameters associated with the intervention(s) that need to be evaluated as part of the initial validation process. These are identified from the selected scientific literature gathered as part of step 1. Not all critical operational parameters described in this literature will be assigned a critical/acceptable limit and eventually be associated with on-going monitoring activities as part of the control measure and be incorporated as part of the written control program. However, all critical operational parameters cited in the scientific support documentation that apply to the design of the validation should be evaluated and documented as part of the initial validation process and thereafter reassessed only as required. For example, installation of equipment may require a specific configuration for the intervention to be effective, however, since it is not a critical operational parameter that will be eventually associated with the control measure (i.e., the operator may not plan to implement on-going monitoring activities for such parameter as part of its PCP), it needs to be only documented in the operator's internal records as part of the initial validation documentation and only reassessed if and when the equipment configuration is extensively modified.
Once these critical operational parameters are identified and incorporated to the PCP, the operator must be able to demonstrate that these same critical operational parameters can be implemented and maintained in actual in-plant processes.
Note that data collection procedures for measuring the critical operational parameters should be similar to those described in the reference scientific/technical literature and, any key measurements should be taken as close to the product contact point as possible, where applicable.
As a matter of principle, it could be acceptable to have proposed critical parameters which would be greater than those listed in the literature as long as these are expected to contribute to the desired outcome. The operator should be able to provide a rationale for doing so and ensure that this practice does comply with other regulatory requirements (e.g., using a higher concentration of a chemical). Additional validation studies are necessary if critical parameters are not implemented in the same or a similar manner by the operator as described in the literature. An example of additional validation requirement could be the intensified microbiological testing to be conducted and documented by the operator to ensure the modified implementation achieves the desired outcome.
b. Microbiological testing data
It is important that the operator gather microbiological testing data, using appropriate indicator organism(s), in order to demonstrate the effectiveness of the intervention or series of interventions. The intervention(s) that the operator has chosen to implement must be capable of reducing a suitable indicator organism by "X" logs under the actual in-plant operational conditions. For example, generic E. coli or Enterobacteriaceae is expected to be reduced by "X" logs by the intervention "Y".
For the purpose of this section, a suitable indicator can be defined as an organism, if present, may indicate the possible presence of E. coli O157. A suitable indicator should share some characteristics with the identified pathogen (e.g., heat resistance, growth range, pH range, ability to grow on selective media, etc.). In the case of E. coli O157, organisms associated with the gastro-intestinal tract of food animals such as Enterobacteriaceae, coliforms, and generic E. coli are appropriate choices for suitable indicator organisms. Indicator organisms recovered by performing aerobic or total plate counts (APCs or TPCs, respectively), have also been used in the scientific literature as possible indicators where microbial counts of organisms associated with the gastro-intestinal tract of food animals are too low and make it difficult to determine statistical significance of a paired study. The operator should have supporting documentation showing that the indicator organism selected is suitable to validate the selected intervention(s). Validation design using more than one indicator organism is strongly recommended.
The evaluation is normally done by comparing indicator levels in a sample taken before and after the intervention(s). It is important to use a statistically significant sample size and time-frame within a defined period (up to 120 days) to demonstrate that the intervention being validated is achieving a targeted log reduction or a statistically significant log reduction while taking into consideration of potential day-to-day variation that could occur within the slaughter and intervention process. For example, an operator of a small volume production establishment cannot sample 15 carcasses during one full day of production and expect this to be considered statistically valid. In this case, it is recommended that the carcasses be randomly distributed and sampled on a weekly basis for a total of 15 weeks.
Carcasses should be randomly selected over the validation period. Days, and hours within a day, should be determined in advance to create a sampling plan. At collection time, carcasses should be selected in a blind manner, for example, sample the 5th carcass after the selected carcass. As a principle, the selection of side A or B should be alternated from one selected carcass in the sampling plan to the next one for the indicator organism testing before the intervention step being validated. This means side A (right or left) should be sampled for the indicator organism testing before the intervention step and side B (left or right) of the same carcass should be sampled after the intervention step. Then, for the next carcass identified in the sampling plan, side B should be sampled first, before the intervention step and then side A, after the intervention step. The operator can refer to the sampling methodology described in the export requirements for the United States (found in Annex T: Testing for Escherichia Coli (E. Coli) in Slaughter Establishments - (ref. 9 CFR Part 310.25 and Part 381, Subpart K)). Note that operators may choose another methodology, for example, sample a larger area, based on the information provided in the scientific literature.
Table 4 is presenting scenarios of potentially acceptable minimum sampling size based on the type of intervention for the purpose of validation testing. Group 1 represents standardized interventions for which the majority of scientific literature exists. These interventions can include automated systems in common use and requires the smallest sampling sizes because of a high degree of consistency of equipment and processes and therefore, a very low variation in the process if managed adequately. Group 2 represents non-automated, modified systems and requires an increase in sampling size because of decreased consistency of equipment and processes when compared to Group 1 interventions. Group 3 represents novel interventions and will require the greatest sampling intensities, including possible microbial testing for the presence/absence of E. coli O157 on a case-by-case basis.
In some occasions, a larger number of samples may be required to establish statistical validity to assure a high level of confidence of the microbial reduction effect of the intervention being validated. An operator may elect to develop a different sampling plan as to what is proposed in this section.
|n for Group 1
|n for Group 2
|n for Group 3
|10 or less
|6 or less
|9 or less
|10 or less
Confidence interval +/- 0.5 log on the difference of indicator organism log counts with 95% Confidence Level
n = Number of beef carcasses to be sampled over a four-month period according to the four-month production volume (N)
N = Production volume (Total number of carcasses) over four months
Group 1 = Standardized intervention, fully automated equipment, for which significant amount of literature/science is available; the operator follows the critical parameters required as dictated by the literature references, for example, steam pasteurizers, mechanical device spraying lactic acid using a specific concentration and temperature.
Group 2 = Intervention that is not fully automated which could lead to an inconsistency in the application of the antimicrobial intervention over carcasses, for example, the application of lactic acid using an hand sprayer; or proposal of a significant modification of a particular critical parameter provided in the literature; or the use of equipment does not have monitoring devices for all critical parameters provided in the literature.
Group 3 = Novel interventions, very limited literature in existence and/or intervention still to be evaluated or approved by regulatory authorities, for example, irradiation of meat products.
- If the lot size, specifically the number of animals slaughtered falls between two values appearing in first column, the highest number should be selected in order to determine the sample size.
- It is the prerogative of each individual company to decide if they want to use an accredited laboratory or not for the testing of indicator organisms. Acceptable methods can be found in the Health Canada Compendium of Analytical Methods.
To assess the efficacy of the reduction intervention beyond chance, it is recommended to use a paired t-Test. The pathway for this statistical test is available in Excel (as an Add-In) under Tools / Data Analysis / t-Test: Paired Two Samples for Means. The Input Variable 1 Range should correspond to the values of EB counts before the intervention. The Input Variable 2 Range should correspond to after EB counts. The Hypothesized Mean Difference should be set to 0, and the Level of Signification (Alpha) to 0.05. Successful interventions should result in a P value inferior to 0.05.
Step 3: Carcass testing for E. coli O157 for establishments validating certain non-standardized and novel interventions.
Because of the expected variability of E. coli O157, and considering the low prevalence of this pathogen in raw beef products, an operator using interventions described as Group 1 or 2 may not need to perform carcass testing on E. coli O157 as part of their validation process, as long as microbial reduction results on carcasses obtained during Step 2 (indicator organisms) are in keeping with the published scientific or technical information and there is a robust day-to-day monitoring and verification system downstream in place to support it. For example, N-60 sampling procedures and results on trims downstream may provide sufficient indication and confidence that the implemented selected intervention is reducing E. coli O157 below detectable levels, and as a result, is working as intended. The operator should be aware that any positive test results downstream during the validation period needs to be carefully analyzed as part of their PCP as this could potentially trigger the need for revalidation of the intervention.
An operator should perform some level of validation sampling on carcasses for E. coli O157 for in depth evaluation of novel intervention(s) in order to demonstrate that the intervention(s) actually achieves a reduction of E. coli O157 to below detectable levels. Operators should develop the data within the initial 120 days of implementing the new intervention or series of interventions, in conjunction with the indicator organism testing on carcasses in Step 2. Any analytic method chosen will be one of the accepted official Health Canada methodologies.
Health Canada's Guidance Document on E. coli O157:H7 and E. coli O157:NM in Raw Beef
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