Listeria presence should serve as a warning that there may be issues that warrant investigation.
USDA-ARS Stephen R Ausmus

The finalization of FDA’s Preventive Controls for Human Food (PC) rule allows FDA to move on to developing guidance. With continued outbreaks and recalls related to Listeria monocytogenes, this is an opportunity for FDA to issue guidance to address this as well.

According to the CDC, Listeria monocytogenes (Lm) is responsible for 1,600 illnesses, 1,400 hospitalizations, and 260 fatalities per year in the U.S. The largest single outbreak of listeriosis occurred in 2011 and was responsible for 147 illnesses, 33 deaths and one miscarriage. The culprit was contaminated cantaloupe from a single farm which affected consumers in 28 states. In May 2000, President Clinton announced a goal to reduce the incident rate of listeriosis by 50% with a target rate of 0.25 cases per 100,000 individuals by 2010. Considerable progress was made and in 2013, CDC reported the incident rate to be 0.26 per 100,000 individuals. The current government-based Healthy People 2020 goal is 0.2 per 100,000 individuals, so there is still room for improvement.

In the most recent Reportable Food Registry (RFR) Annual Report (published in May 2014 for September 2012-September 2013), FDA identified Lm as responsible for 17.33% of all 35 primary RFR entries, which is actually down from 48 the reporting year before. The contaminated products ran the spectrum of commodities, including seafood, produce, dairy, nuts, bakery, and prepared foods. In the last year or so, Lm illness outbreaks and recalls have repeatedly captured media attention.

The final PC rule requires that facilities that manufacture ready-to-eat (RTE) foods that are exposed to the environment post processing evaluate the risk of environmental pathogens, namely Salmonella or Listeria. If the risk requires a preventive control, the facility will likely also need to implement an environmental monitoring program. But since the rule doesn’t prescribe how such a program would be structured, there are varying perspectives regarding the definition of a robust program and concerns about how FDA will react to a facility finding a positive result for Listeria.

When it comes to environmental monitoring programs, the topic of greatest debate is whether facilities should test zone 1 surfaces (also called food or product contact) for Listeria species. Individuals who are primarily regulated by the USDA Food Safety Inspection Service (FSIS) generally have a very different perspective on zone 1 testing than those who produce FDA-regulated products. Is the science different? No. But, historically, the policies of the different agencies have been different.

With the finalization of the PC rules, FDA will be issuing new guidance on environmental monitoring for Listeria. We’re hopeful that this will provide an opportunity for FDA to align with the FSIS approach. But until guidance is issued, there are a few points about an environmental monitoring program of which we are fairly certain.

  1. Facilities need to have a robust environmental monitoring program that finds Listeria (i.e. yields “positive” test results). If one never finds anything, it’s an indication that the facility is probably not looking hard enough or in the right places.
  2. When (not if) a positive result is found, corrective actions that eliminate those positives must be taken, and appropriate retesting is needed to ensure the corrective actions accomplished the mission.
  3. Solid documentation surrounding the entire process is critical.

Let’s explore the current state of play:

THE SCIENCE. When talking about this pathogen, it’s critical to differentiate Listeria species from Lm. The genus Listeria contains at least seven species, only two of which are pathogenic to humans: Lm and very rarely L. ivanovii (an opportunistic pathogen). From a public health and regulatory standpoint, Lm is a pathogenic species of concern in the family of Listeria. Listeria can persist in the environment and grow under refrigeration conditions. These characteristics make Listeria species a good indicator organism for Lm, and its presence should serve as a warning that there may be issues with cleaning and sanitation, traffic patterns, infrastructure/construction, etc. that warrant investigation.

FSIS APPROACH. When FSIS-regulated products topped the list of the 2003 joint risk assessment for listeriosis, the agency reconsidered how to encourage proactive industry efforts to control Lm. The approach included risk-based requirements for testing the environment, including product contact surfaces, for Listeria species. FSIS determined that if a RTE product or food-contact surface tests positive for Lm, Salmonella, or other pathogen of public health concern or its toxins, the product from the tested lot or product that passed over the food-contact surface is considered adulterated. But, if a product passes over a surface that tests positive for Listeria species, the product is not summarily considered adulterated, and the establishment is not required to confirm whether the sample is positive for Lm. However, the establishment is required to take corrective action with respect to the food-contact surface.

FDA APPROACH. In 2008, FDA published draft guidance clarifying its expectations for environmental monitoring programs. If finalized, the guidance would recommend, but not require, testing of critical surfaces: at least weekly for critical food-contact surfaces and biweekly for critical non-food-contact surfaces. Unlike FSIS, FDA would treat a critical food-contact surface that was Lm positive differently if the implicated food supports the growth of Lm. (Lm will not grow in frozen food, where the pH is 4.4 or less, or where the water activity is less than or equal to 0.92.) If the food supports the growth, FDA recommended in its 2008 draft compliance policy guide, that the food be treated with a listericidal control measure, reprocessed so it will no longer support the growth, ensuring that the food contains less than 100 cfu per gram, or be diverted or destroyed. If the food does not support the growth of Listeria, FDA recommended the food be treated with a listericidal control measure, that the level of Lm be quantified, and that any food with more than 100 cfu Lm per gram of food be diverted or destroyed. However, the draft guidance also stated that a firm testing for Listeria spp. (as opposed to Lm) would need to speciate the organism to determine if it was Lm or assume that it was Lm. The effect of this policy is that FDA-regulated firms testing zone 1 product-contact surfaces need to hold product pending the result of the test. If the result is positive, they need to hold the product longer while determining if the organism is Lm or discard the product. This differs from the FSIS approach and serves as a disincentive for industry testing of zone 1 surfaces.

A HARMONIZED APPROACH? There are promising signs of a possible unification of the agencies’ approaches, which should result in a more consistent industry approach.

At the December 2015 meeting of the FDA Food Advisory Council, Listeria was the sole topic of discussion for the entire two-day meeting. FDA and FSIS representatives talked through their historical approaches and expressed their desire for a harmonized approach to environmental monitoring that would encourage rather than deter aggressive industry testing for Listeria. In a pre-meeting announcement, FDA stated, “The public health and regulatory challenges posed by Lm have bedeviled FDA and industry since at least 1996, when the agency established a zero tolerance for the presence of L. mono in cooked RTE foods. Subsequently FDA issued draft guidance documents in which it signaled that it was considering softening that stance for RTE foods that do not support the growth of L. mono, based on a risk assessment and follow-on analysis suggesting that such foods presented a lower risk of listeriosis.”

A move away from zero tolerance certainly would have been welcomed by affected segments of industry. However, recent developments now have FDA rethinking whether a move away from zero tolerance would be adequately protective of “the most vulnerable individuals in at-risk subpopulations.”

Another part of the announcement stated, “FDA is concerned that our recommendation, in the 2008 draft Guidance for Industry (GFI), to determine whether an indicator organism (Listeria spp.) detected on a food-contact surface is actually the pathogen (i.e., L. monocytogenes) may have discouraged the development of robust Listeria control programs. FDA is considering changing its recommendation on when a firm should determine whether Listeria spp. that is found on a food-contact surface is the pathogen, L. monocytogenes.”

In addition, there was discussion on:

  • If frozen vegetables and foods that appear to be cooked should be considered RTE, even if they bear cooking instructions.
  • The need to generate data to help FDA distinguish between contamination of produce with Lm that could occur in packinghouses versus contamination originating in a growing area.
  • Whether FDA should change its sampling priorities, which are currently biased toward increased sampling of foods that support the growth of Lm.

What’s next? The Alliance for Listeriosis Prevention, which consists of more than a dozen trade associations, is anxiously awaiting the release of FDA’s revised guidance on environmental testing. Once published, the guidance will be open for public comment, and we will coordinate efforts to review and respond to a request for feedback. Watch for an ALP-organized webinar to review highlights of the document shortly after it is released – which is probably several months away. In the meantime, we hope that FDA considers aligning its forthcoming guidance with FSIS to encourage aggressive testing for Listeria.

The authors: McEntire is vice president, science operations, GMA; Detlefsen is senior vice president, environmental and regulatory affairs & staff counsel, National Milk Producers Federation.