Ask the Expert January 2018

EAS Webinar on FDA Draft Guidance: “Control of Listeria monocytogenes in Ready-To-Eat Foods: Guidance for Industry” October 31, 2017

EAS received an overwhelming response to our recent webinar on controlling Listeria monocytogenes in ready-to-eat foods. As a service to the industry, we thought it would be helpful to provide some of the questions generated by webinar participants answered by EAS Senior Director for Food Consulting Services, Allen Sayler. Please understand that these responses do not constitute consulting advice. Should you have questions or require clarification based on your own company’s situation, please reach out to Allen at

Webinar Participant Questions & Answers:

  1. Can comprehensive, high sample rate finished product testing be used in place of FCS swabs? Answer: Unless the finished product testing protocol is statistically valid, it is strongly recommended that ATP swabbing is utilized on clean and dry FCS. A calibrated ATP system can provide results within 1 minute and allow the sanitation crew to reclean and re-swab the FCS to ensure it has been effectively cleaned. This approach is “preventive” versus a finished product sampling plan which is “reactive”.
  2. What do you recommend for a processing plant that produces RTE foods but during processing, there is no exposure to the environment, prior to packaging? Such as our products are in an enclosed system from Raw Material tank to Mixing tanks and to Finished Good tank. Is 21 CFR 117.130 (c)(1)(ii) fully applied?Answer: 21 CFR 117.130 (c) (1)(ii) states the following:“The hazard evaluation required by paragraph (c)(1)(i) of this section must include an evaluation of environmental pathogens whenever a ready-to-eat food is exposed to the environment prior to packaging and the packaged food does not receive a treatment or otherwise include a control measure (such as a formulation lethal to the pathogen) that would significantly minimize the pathogen.” We are of the opinion that all food processing plants, regardless of whether the product is protected from the environment prior to packaging, need some type of environmental monitoring program.
  3. Is there guidance on what “exposed to the environment” means? What about products that are processed in closed system post killing step, then packaged? Answer: The phrase “exposed to the environment” needs to be taken intuitively. However, based on the answer to #2 above, it is not necessary to “dial-in” term “exposed to the environment” as we are of the opinion every food processing plant should have an environmental monitoring program.
  4. Is the recommendation to test Listeria species or monocytogenes for all four zones and finished product testing for RTE foods? Answer: It is not practical or financially possible to establish a finished product testing protocol for RTE foods that is statistically valid. Therefore, a limited finished product testing program that describes taking at least one sample for each days’ production or for each production lot would provide an adequate finished product testing program. It is our opinion that for those processing environments that are associated with moist conditions or the use of water for cleaning the floors, outside of processing equipment, etc.; an environmental monitoring program should be based on detecting Listeria species, with swabbing concentrated on Zone 3 (floors, walls, door knobs, floor drains). Zone 2 should only be included if there is a positive Zone 3 swab and there is need to use vectoring to identify the true source. For relatively dry processing environments, it is recommended that Salmonella be the choice for detection of environmental contamination. It is strongly recommended that ATP swabbing is utilized on clean and dry FCS (Zone #1). A calibrated ATP system can provide results within 1 minute and allow the sanitation crew to reclean and re-swab the FCS to ensure it has been effectively cleaned. This approach is “preventive” versus a finished product sampling plan which is “reactive”.
  5. Is there a good number of vector sponges to take when finding a Listeria hit? Answer: The simple answer is enough to identify the true source of any positive environmental swab, particularly if the positive was found in a floor drain or on a floor source. Some industry “vectoring” plans take swabs at pre-set distances from the source in quadrants. An example might be 5 feet intervals at 0°, 90°, 180°, and 270°. These samples will provide information on the best direction to continue to gather environmental swabs to identify the true source of the environmental contamination.
  6. When an FCS is tested for Listeria, is the recommendation still that all finished product be placed on hold until a negative test result is confirmed? (For all finished product from the production run in progress when FCS testing was performed). Answer: While there is no requirement by FDA, it is common industry practice that whenever any FCS is tested for Listeria(species or monocytogenes), finished products that contain anything that came into contact with the tested FCS be put on hold until such time as the results of the swabbing are known. If such product were to be released to customers or consumers and the FCS swabbing came back positive for Listeria, then an immediate Class I recall with a public press release would be the likely outcome. Utilizing ATP swabbing technology is a much more effective way to routinely detect and correct unclean FCS.
  7. What would you recommend that facilities producing RTE products with a short shelf life (produce, packaged salad kits, etc.) approach Zone 1 testing?Answer: See the answers to #1, #4 & #6. It is our opinion that there should be no direct environmental swabbing of Zone 1 for Listeria or any other human pathogen. ATP technologies work much better and provide an almost immediate feedback so the unclean FCS can be recleaned and sanitized prior to any contact with food ingredients, food packaging or the food itself.
  8. Do these new guidelines apply to frozen vegetables? Answer: In Section III of the draft Guidance document, any process (freezing) needs to be validated to determine whether there is a listeristatic or listericidal effect that will demonstrate that the food is not adulterated. While frozen vegetables originate from fresh produce covered by the FDA FSMA Produce Safety regulation, microbiologically, the Listeria bacteria is not killed by freezing but does not reproduce (listeristatic). Once frozen vegetables contaminated with Listeria is thawed, Listeria starts to grow and become a human health threat so yes, the FDA draft Guidance would also apply to frozen vegetables. On page 32 of the draft guidance, it states the following, “Many foods are stored in a frozen state – e.g., to extend shelf life before retail sale or as a product available to consumers in the frozen state. L. monocytogenes does not grow at temperatures below freezing (Ref. 12 and Ref. 13). Therefore, freezing is a particularly effective temperature control measure to prevent growth during storage. Freezing will not eliminate L. monocytogenes from foods and cannot be relied upon as a control measure for the elimination or reduction of Listeria monocytogenes.”
  9. How does FDA define finding Listeria spp or L. mono. “on occasion?” In other words, what is “too high” a rate of detection. Answer: We are not aware of any FDA-based numerical definition of finding Listeria “on occasion”, or what is “too high” a rate of detection of Listeria in environmental swabs. Of much more importance to FDA and to customers and consumers in general, is the corrective action follow-up and root cause analysis conducted to identify the true cause of the positive Listeria swab and adjust manufacturing operations to eliminate the real source of the contamination.
  10. What is the FDA expectation of Listeria levels in a plant? Answer: We are not aware of any FDA-based numerical expectation of what might be an “acceptable” number of Listeria swabs being positive versus negative. What is of more importance is the frequency of re-occurrence and response to positive samples. If the same swabbing location was positive for Listeria every other month for 6 months, then that indicates a failure to identify the true root cause. We are aware of an unpublished and non-scientific practice where more than 3 positive in 100 samples, regardless of location, may indicate a more thorough corrective action effort is needed. It is very important that all environmental monitoring results be incorporated into some type of trend analysis to determine if patterns of positive results exist that need additional attention.
  11. How does the FDA Draft Lm Guidance relate to the FDA Food Code and application in the retail grocery environment? Answer: All FDA guidance documents represent FDA’s current thinking on a topic. Many times, this guidance is intended to clarify the section of an FDA law or regulation. The draft guidance specifically states that it is not intended to be applicable to retail food operations. The Retail Food Code (applicable to grocery stores and restaurants) is utilized by FDA to provide the requirements for retail food operations. It is essentially a Public Health Code or model, not an FDA law or regulation, intended for adoption by states, counties and local governments. Modification of the Retail Food Code must be done through submittal of proposals to the Conference on Food Protection, which meets approximately once every two (2) years to consider new proposals.
  12. What is the FDA perspective on the risk associated with finding L. monocytogenes in the environment in raw vs. RTE areas? Answer: We are of the opinion that FDA is utilizing a positive environmental swab result for L. monocytogenes in “raw” areas of the processing facility as evidence that this source could find its way into the RTE areas of the processing operations. They are very likely to intensify their efforts to identify L. monocytogenes in RTE areas. If none is found, FDA is likely at a minimum to note the positive L. monocytogenes result in their Form FDA 483 observations.
  13. Is FDA focusing in finding Listeria in raw areas, while using Whole Genome Sequencing, even if processing facilities have implemented adequate raw-RTE separation and controls? Answer: FDA is utilizing pulsed-field gel electrophoresis (PFGE), multiple locus variable number tandem repeat analysis (MLVA), and whole genome sequencing (WGS) as the main tools for the PulseNet’s fingerprinting of food pathogens. It is our understanding that all positive environmental swabs that detect a foodborne human pathogen are analyzed using PFGE at a minimum, regardless of the location of the swabbing.
  14. Does the guidance doc require zone 1 sampling 3-4 hours into production? Or is that for zone 2 and 3? If it is zone 1, what kind of swabbing is required? Listeria spp? or L. mono.? Answer: An FDA Guidance document cannot “require” anything, but as stated in the answer to #11 above, it is the Agency’s most current views. FDA field investigators are not authorized to enforce any FDA Guidance documents but can use the information in such document as a benchmark to measure whether the industry is taking reasonable precautions to ensure their food is safe. On page 37 of the draft guidance, there is a reference to taking environmental samples 3 – 4 hours after the start of production. On page 36 of the draft guidance, it states, “We recommend that even the smallest processors collect samples from at least 5 sites of FCS and 5 sites of non-FCS on each production line for RTE foods. We recommend that larger processors determine the appropriate number of sampling sites based on the size of the plant.”It is our opinion based on answers to previous questions, that any environmental swabbing is conducted primarily on Zones 3 for the detection of Listeria species. This is not the recommendations from FDA found in the draft Guidance document, which states on page 37,
    • Collect environmental samples from specific FCSs on the production lines at least once every week when the plant is in operation; and
    • Test each FCS in the plant at least once each month.
  15. Does the recommendation to test Zone 1 for Listeria apply to high-risk foods only? Do you expect Zone 1 to be tested in low moisture/Aw food plants? Answer: Based on the current statements in the draft Guidance, FDA appears to be making no differentiation between low-risk, medium-risk and high-risk foods regarding the recommendation to gather environmental swabs for FCS (Zone 1).
  16. What is more powerful? Testing finished product based on ICMSF N=20 or more samples or zone 1 testing (but not test finished products)?Answer: A Zone 1 (FCS) positive test for L. monocytogenes should be considered the same as a positive finished product test. It is our opinion that the preferred testing program for RTE food manufacturers focuses on environmental testing as a means to implement preventive controls rather than finished product testing, which is a reactive approach. Sampling should consist of:
    • A credible number of environmental swabs taken primarily in Zone 3, and
    • Effective corrective actions including additional environmental samples and vectoring for any positive environmental samples, and
    • Utilization of ATP swabbing at every production start-up on a representative number of FCS and immediate recleaning if the calibrated ATP result is “positive”, and
    • Accumulating a set of retailed finished product samples (one from each production lot) and storing these to the end of the shelf life of the finished product, and
    • Test a minimum number of finished product samples (one per production run or production day) for foodborne pathogens, which for most foods would be L. monocytogenes and for dry foods, Salmonella.
Posted in 2018 January, Ask the Expert.