Swabbing for Actionable Results

Typically, the COAs would arrive around 4:30 a.m. With the anticipation of the smart phone notifying me that I’ve received an email, that anxious question of “What are the results?” would begin circling in my mind. As I lay in bed with blurred vision from having just awoken, I begin to open the attachments, enlarging the screen view as I scroll through the reports looking for that dreaded word “Presumptive.” Most of the time, the anxiety is assuaged with results of “Negative” met by a sigh of relief. On occasion, that dreaded result is printed, right there, clear as day, mocking me with contempt as if to say, “Catch me if you can!”

This opening likely describes the reality for many food safety professionals as they determine corrective actions and root cause analysis required by their Food Safety Plans and sanitation preventive controls. Additionally, for those segments of the industry that do not have the benefit of a process kill step, the magnitude of determining root cause becomes much more arduous if surfaces are swabbed during the course of production (operational swabbing), as recommended by FDA in its recent Listeria draft guidance.

When the manufacturing process includes a kill step, a positive test result associated with a food contact surface (FCS) or the product itself can confidently be traced to an issue in the post kill-step environment. The same logic does not carry through in the case of whole or fresh-cut processing, however.

Listeria spp. including Listeria monocytogenes (Lm) is a natural part of the outside environment where most fresh produce generally grows. This makes the interpretation of ingredient, environmental monitoring, and finished product testing results very difficult for fresh produce operators who have no listericidal treatment in their operations.

United Fresh Produce Association Vice President of Food Safety & Technology Jennifer McEntire explains support of this concept as: “Fresh produce lacks a kill step. Given the ubiquity of Listeria spp. in the natural environment, it is impossible to ascertain if a Listeria finding in raw material upon receipt, or a product contact surface, or a finished product, was due to an issue in the facility or in the field.”

When the Produce Safety Rule was first proposed, FDA stated in the preamble “an intact fruit or vegetable could reasonably be expected to occasionally be positive for L. monocytogenes. Many studies have shown the presence of L. monocytogenes on fresh, intact produce, but there is limited epidemiological evidence associating Listeriosis with produce, especially with intact fruits and vegetables.” The preamble goes on to cite several references.

With this knowledge and understanding, an investigation into a “presumptive” result (raw material, environmental, or finished product) could be inconclusive in terms of the root cause, making a corrective or preventive action nearly impossible to ascertain.

Utilizing the direction of FSMA’s Risk Based Preventive Controls, the hazard evaluation and the environmental monitoring program should be linked, which guides the implementation of measures (such as where and when to swab) on the basis of risk. The objective of a Listeria control program in a fresh produce operation should be to prevent harborage and the introduction and cross contamination of additional L. monocytogenes.

With the “reasonable” expectation of an occasional Lm on intact fruits or vegetables and the objective to prevent harborage or further introduction, swabbing the FCS operationally in a whole or fresh-cut processing facility can yield a result to which there is no reasonable corrective action.

So, to have results that can be effectively acted upon, we need to ensure our search is designed to identify actionable results to directly prevent niche exposure, introduction of Lm, and cross contamination. To reach this goal, the timing of the food-contact swabbing should be considered.

Swabbing an FCS in a whole or fresh-cut produce facility can provide an actionable result as long as the swabbing is not done operationally while running product that could, itself, transfer a transient pathogen to the FCS. Actionable results lie within the effectiveness of the sanitation program, in the absence of product. Swabbing for Listeria spp. on equipment that has been washed (prior to sanitizing) and prepared for production use is one of the best indications of effective sanitation.

An effective sanitation program is not just the responsibility of the sanitors or the sanitation professionals that clean the equipment. There are many inputs that directly impact the success and goals of effective sanitation, such as condition of equipment, sanitary design, time allowed for effective cleaning, and proper chemical usage, to name just a few.

Engaging in an effective pre-operational FCS swabbing program will yield results that are actionable and verify that the sanitation program is able to prevent pathogenic niche harborage, introduction and cross contamination. There are many elements of an effective swabbing program to consider, some of which include operating the equipment in the absence of product to allow for any niche areas to be “worked out” and found on the equipment. Deep cleaning and routine equipment tear-down procedures also are included in an effective swabbing program following a risk assessment and verification of SSOPs.