The Food and Drug Administration (FDA) has recently proposed changing the regulations on Listeria monocytogenes in ready-to-eat products. It is important to keep in mind that this proposed change would only apply to foods regulated by the FDA. The change would create two categories of ready-to-eat foods: those that support the growth of Listeria, and those that do not support the growth. For foods that do not support the growth of Listeria, the foods would not be considered to be adulterated unless the population of Listeria monocytogenes exceeded 100 colony-forming units (cfu) per gram. For foods that do support the growth, the present standard of 1 cfu in 25 grams would still be considered adulteration.

The FDA defines foods that do not support the growth of Listeria as those which meet one of the following criteria:
• pH less than or equal to 4.4,
• commonly held frozen,
• water activity less than or equal to 0.92,
• incorporates a process or ingredient which effectively inhibits the growth of the bacterium.

Within the regulatory purview of the FDA, some examples would include but not be limited to frozen foods, ice cream and some cheeses. If USDA-FSIS were to put forward a similar proposal, many processed meat and poultry products could potentially meet at least one of the criteria and qualify as a food that does not support the growth of Listeria.

Listeria has been a vexing issue for all manufacturers of ready-to-eat foods, and not just those who manufacture meat and poultry products. Because of its wide distribution in nature and its ability to survive in a variety to environments, Listeria contaminates ready-to-eat products after processing all too frequently. Although the number of human cases of foodborne listeriosis is relatively small, the regulatory focus is justified because of the high mortality associated with the illness. The mortality rates of foodborne listeriosis rival those of botulism. If the proposed change is implemented and there is an increase in human foodborne listeriosis, it is almost certain that the regulations would be changed back to the current standard.

The FDA’s proposal to change the status of Listeria monocytogenes in foods that do not support the growth of the bacterium is based on good science, and many would argue that this is long overdue. Many other countries, including Canada and those in the European Union, adopted a similar approach many years ago. Based on the available information, this approach appears to achieve the goals of protecting public health while not imposing an undue burden on food processors. While there can be no compromise on protecting public health, there appears to be little to be gained by imposing a presence/absence standard on foods that do not support the growth of the bacterium.

The FDA currently has its proposal open for public comments. While there will certainly be those who oppose the change for many reasons, we hope that the FDA will be successful in implementing this change. We hope that USDA-FSIS will follow FDA’s approach to changing the regulatory structure of Listeria monocytogenes in ready-to-eat meat and poultry products which do not support the growth of Listeria.

To contact James S. Dixon, call (515) 294-4733, email or write to him at Dept. of Animal Science; 215F Meat Laboratory; Iowa State University; Ames, IA 50011.