Swab samples taken by the Food and Drug Administration (FDA) are intended to find pathogens, if present: Salmonella, Listeria monocytogenes, or pathogenic Escherichia coli. These are three pathogens to put fear in the strongest food safety professional. I recently left a food facility where we discussed all three. If Salmonella is the old, and L. monocytogenes is the current, then pathogenic E. coli is the future.
Every Salmonella is pathogenic. Some Salmonella are associated with their source, like turtles and chickens. The majority of foodborne illness is caused by just ten out of thousands of serovars of Salmonella. When we come across a Salmonella that is not among the top ten, we take note. That was the case with the Valley Milk recall. Salmonella meleagridis was identified. This one is rare. What does that mean? It means it was unique to the product and environment. Since it is unique, it may be able to be traced to a source. All Salmonella patient isolates are tested by whole genome sequencing (WGS) and are in the PulseNet database. If there are any patient isolates of Salmonella meleagridis, the Centers for Disease Control and Prevention (CDC) will investigate the link between the patient and consumption of food with the contaminated milk product.
What is an isolate? In a sample of patient fecal matter, finished product, raw ingredient, or environmental swab there is a variety of microorganisms, mostly harmless. When the lab pulls out the pathogen from among millions of other cells, the pathogen is grown as a pure culture. This is the isolate. This is also why microbiological testing takes time. Our lab tests are designed to find one pathogenic cell among millions of harmless cells.
Salmonella is big deal. An estimated one million cases of salmonellosis occur every year in the United States. Where will FDA test your facility for Salmonella? FDA will sample dry ingredient storage, dry blending, and “dry” operations. Roasting and grinding of nuts are dry operations. Nut butters and oil-based products are made in a dry area, i.e. where there is no use of water. The facility I just left was a wet operation, except for one product where they had a dry seasoning. When FDA swabs, they could test that one area for Salmonella. For the most part, FDA is not currently focused on Salmonella. The exception to that is manufacturers of products in an industry where there have been recalls, like peanut butter.
Keep your ears open for recalls by your competitor. You can sign up for recall alerts.
Listeria is the current favorite of the FDA and CDC. For example, there was an FDA initiative to visit raw milk cheese plants for swabbing. Other foods are not immune. FDA is going to facilities and conducting intensive swabbing. When the FDA arrives with a handful of inspectors, over 100 environmental sites will be swabbed from zones 1, 2, 3 and 4 per day. Product samples will be taken. My advice is to hold all product made on those days until Listeria tests are negative. Negative results should be reported within days. If Listeria tests are presumptive, consider discarding the product. However, be prepared to wait weeks for FDA to communicate results. What do you do if you can’t hold your product? Discard it. Limit the runs on the days the FDA is swabbing. Document the disposition of the product, in case the results come back positive. Companies have decided to simply discard perishable finished product made during these inspections, rather than wait for results.
Why wait for the FDA to show up for swabbing? My advice is to conduct your own intensive swabbing exercise. Know the areas of your facility that are hot for Listeria. Do you have to test product? No. Do you have to test zone 1 for Listeria? No. For zone 1 food contact surfaces, I recommend Enterobacteriaceae counts. You could do coliform or E. coli testing instead of Enterobacteriaceae. Do you have to test for Listeria monocytogenes? No. You can test for Listeria genus. Of the 17 species of Listeria, only L. monocytogenes is pathogenic. Getting a positive Listeria genus test means the environment is conducive for L. monocytogenes.
There is a difference between Listeria genus and Listeria monocytogenes testing. First, you will get the Listeria genus results quicker. Second and if you stop testing at Listeria genus, you will not have direct documentation of the presence of L. monocytogenes, the pathogen. The key is in your corrective action. Your corrective action might be the same whether the test is a presumptive Listeria genus test or a positive L. monocytogenes test. In other words, treat the seriousness of a presumptive Listeria genus the same as a positive L. monocytogenes.
The FDA published the draft Listeria guidance in January 2017. The guidance is currently in its comment period. All draft guidance represents the FDA’s current thinking on a topic. While not mandated, FDA expects industry to conduct environmental monitoring for Listeria when ready-to-eat (RTE) foods are manufactured. There is even greater FDA scrutiny for RTE foods which can support the growth of Listeria. We are anticipating another FDA guidance document to further define RTE foods. In the meantime, refer to the Preventive Controls Hazard Guide; it is 185 pages. There are categories of food, their hazards, and examples of food in the category. This is FDA’s current thinking on hazards in food. If the food is categorized as RTE, the facility should have a Listeria environmental monitoring program.
Do you need help in designing your environmental monitoring program? I would love to help!
Every isolate of L. monocytogenes from a patient has been sequenced by WGS and is in the PulseNet database. This fact keeps food safety professionals up at night. The FDA can pull a food from the grocery shelf, isolate L. monocytogenes, inform the company to initiate a recall, and match the food isolate to a patient isolate. Check out my previous post, What I want all my students to know about Listeria.
Most E. coli are not pathogenic. We can test on-site at a food facility for Enterobacteriaceae, coliforms, or E. coli and not be in fear of growing billions of cells of pathogenic E. coli. For now, what you need to know is that patient isolates of pathogenic E. coli will be sequenced by WGS and be in the PulseNet database. In the same way that Salmonella or L. monocytogenes can be matched from food isolate to patient isolate, so will pathogenic E. coli be matched. The technology and laboratory expertise are there.
It is somewhat comforting to know that that while the number of recalls is increasing, the number of cases, i.e. patients, is decreasing. The food industry is making great strides in food safety. Because of greater surveillance and communication, the average number of cases (patients) per outbreak has decreased. The number of multi-state outbreaks has increased for the same reasons.
There is much to be hopeful about around food safety. Job security is one!
Dr. Kathy Knutson has food safety expertise in microbiology, hazard analysis, and risk assessment. As a recovering academic, she resides in Green Bay home-of-the-Packers, Wisconsin with her brilliant husband and two handsome sons. Learn more about her consulting services at https://www.linkedin.com/in/kathyknutsonphd.