Both FDA and FSIS have regulations related to L. monocytogenes in ready-to-eat (RTE) foods. FSIS has a zero-tolerance policy for L. monocytogenes on RTE meat products within its regulatory purview, such as hot dogs and luncheon meats (FSIS, 2003). Until FDA published proposed draft guidelines in 2008 that established two categories of RTE foods, it had a zero-tolerance policy for L. monocytogenes in all RTE foods within its regulatory purview. Under those zero-tolerance policies, the presence of L. monocytogenes indicated the product was “adulterated” and unfit for commerce (FDA, 2008a).

The food industry argued that not all RTE foods support the growth of L. monocytogenes equally and, therefore, that not all RTE foods should be subject to the same regulations. The food industry identified low pH, low water activity, and the presence of an “inhibitory” substance as factors that inhibit the growth of L. monocytogenes. The industry also argued that the risk of listeriosis depends on the type and frequency of RTE consumption as well as on home refrigeration factors (i.e., temperature and duration). In essence, the industry was arguing that the variability in food susceptibilities and the uncertainty in home refrigeration had not been considered in the regulations.

In light of those arguments, FDA reviewed its zero-tolerance policy for L. monocytogenes. The agency was faced with determining whether or not to relax the zero-tolerance standard for some foods and, if they were relaxed, what guidance it should issue to industry for controlling L. monocytogenes (FDA, 2008a).

Human Health Risks

The 2003 FDA/FSIS risk assessment was designed to predict the relative risk of listeriosis from eating certain ready-to-eat foods among people in three age-based groups: perinatal (16 weeks after fertilization to 30 days after birth), elderly (60 years of age and older), and intermediate-age (general population, less than 60 years of age) (FDA and FSIS, 2003a,b). The assessment evaluated 23 categories of foods considered to be the principal potential sources of L. monocytogenes. In particular, it evaluated the heterogeneity among different foods and different age groups of people. Consistent with previous assessments, the 2003 assessment concluded that foodborne listeriosis is a moderately rare but severe disease, and it supported the findings from epidemiologic investigations of sporadic illness and outbreaks of listeriosis that certain foods (for example, pâté, fresh soft cheeses, smoked seafood, frankfurters, and foods typically purchased from deli counters) are potential vehicles of listeriosis for susceptible populations.

The assessment estimated the human health risks for different exposures. It also used various scenarios—different food consumption rates,

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