Listeria Confusion Hurts Consumers and Companies

I did my doctoral research on Listeria monocytogenes. Never could I have imagined the continued misunderstanding that results in catastrophic outcomes for consumers and companies.

Let's review a few key points around which I see continued confusion:

• There are many Listeria species. L. monocytogenes is the primary pathogen of concern for human health.

• Finding Listeria spp. does NOT mean monocytogenes exist (Before 2017, the FDA essentially took the stance that if you couldn't prove it wasn't mono, you had to assume it was. So, people didn't test. Now, FDA guidance acknowledges that finding Listeria species does NOT mean you have mono).

• "Seek and destroy" should be encouraged. And "destroy" means destroying not only the organism's presence but also the conditions that allowed it to exist (e.g., don't just throw sanitizer on the spot; address the crack in the floor or the rough weld that serves as a growth niche.)

• You may need to vector out from the original positive to find that harborage site—your original positive might just have been a stop on its journey, so a follow-up negative could be misleading.

• Corrective actions are key. Table 6 in FDA's Listeria guidance should dictate your actions.

  
  

There have been several recent situations that suggest that aggressive testing for Listeria spp. is discouraged-- and several outbreaks and recalls that illustrate the consequence or the fear of looking for Listeria.

1. A recently posted 483 (the form FDA uses to document objectionable 'observations' during a facility inspection) criticized a firm for finding Listeria spp. This should be celebrated (as long as appropriate corrective action is taken), not penalized! FDA does not explicitly require environmental monitoring for Listeria nor prescribe how or where to sample. So, I fear that other firms will look at this 483 and decide that the "safer" thing to do is not to test at all or in a way that guarantees you won't find it. There are way too many examples of this occurring. Not finding Listeria doesn't mean it's not there. While I haven't seen the environmental monitoring programs of every firm associated with L. monocytogenes-related recalls and outbreaks, these plans were clearly inadequate. Is the fear of finding a positive to blame? A regulatory reprimand for Listeria's findings disincentivizes "seek and destroy."

2. At the International Fresh Produce Association, I helped develop a mentored online Listeria training program built upon the United Fresh in-person training (inspired by the Meat Institute's longstanding Listeria training). I was a mentor for the most recent class and am concerned about the continued belief that zone 1 (food contact surface) testing for Listeria spp. must be avoided since a positive renders the food adulterated. This is not true!

3. I recently worked with a firm that had tested Zone 1 for Listeria spp. after running fresh produce. While FDA guidance suggests Zone 1 be tested 3-4 hours into production, this approach should be avoided for fresh produce companies and other products that lack a kill step. When the firm got a positive, it was impossible to discern if it was due to a harborage in the equipment or was introduced by the product. Environmental monitoring programs should be structured for clear follow-up (running without the product is one option).

4. Another client saw repeat positives in Zone 3 but feared vectoring into Zone 2. Fear shouldn't influence your EMP.

5. Another firm hasn't been able to find a positive, even going out to Zone 4. This is suspect. If you can't find a positive, the program should be reconsidered. This includes a reevaluation of sampling sites, timing of sampling, the sampling approach, buffers, enrichment, and detection methods.

6. In the past year, we've seen a few outbreaks where the strain in the production environment matched the outbreak strain. Whole Genome Sequencing allows what used to be "one-off" illnesses to be connected and recognized as part of an outbreak - even years later. Issues that flew before the radar are more likely to be found today. Someone will find it if it's there—in the product or in the environment. Better you than a regulator.

   
   

Solutions

FDA maintains a "zero tolerance" for Listeria monocytogenes in ready-to-eat foods. Given that rates of Listeriosis have not changed for decades, the industry is not achieving zero.

So, what can be done? Test Zone 1 food contact surfaces. Intelligently. Aggressively. Here's what I believe is needed to make this a reality.

 Buyers should encourage Zone 1 testing of Listeria spp. 

• Some direct their suppliers to avoid testing Zone 1

• Some buyers require suppliers to notify them of a positive. If suppliers fear the repercussions of finding Listeria spp., they will not test appropriately.

• If a buyer learns that their supplier had a positive on Zone 1, they should not assume that it's mono and move forward with a recall. This is not a recall situation.

Regulators and auditors should not penalize firms for occasional positive findings.

• Place more emphasis on trends and corrective actions. The goal of the EMP should be to find those parts of a plant where Listeria can hide, and get rid of them. I’ve seen a real underemphasis on corrective actions.

Auditors should not be directing the firm's EMP. Too many times I see very poor EMPs and when asked, the client replies that it was adjusted based on what the auditor wanted to see. This is insanity. Food safety professionals should have enough sense to write their own plans and be able to defend them. And if they don’t, they need to be trained on this.

The number of inadequate EMPs I have reviewed is concerning. The root cause seems to be a lack of fundamental understanding of Listeria as an organism, and severe misunderstandings about regulatory policy. In addition, EMPs often miss clearly spelling out the cascade of actions that should occur after finding positives (See Table 6 referenced above). The outcome is an inadequate EMP, resulting in recalls, outbreaks, and impacts to customer relationships.

We need to change our minds and change our approach to Listeria management. There are many changes that firms can make today. There are ongoing discussions around additional policy adjustments to further encourage finding Listeria with the goal of eradicating it. Anyone responsible for developing or reviewing an EMP should be extremely familiar with the FDA Listeria guidance and the various industry guidance documents that tailor the FDA recommendations for a specific commodity. If not, reach out to us or your trade association for help.