Achieving Continuous Improvement In Reductions In Foodborne Listeriosis – A Risk Based Approach

Listeria monocytogenes is a foodborne pathogen that can cause listeriosis, a severe disease whose symptoms include septicemia, meningitis, and spontaneous abortion. Ongoing efforts are needed to further reduce the incidence of listeriosis, due to its high mortality rate. The focus of this report is the use of a risk-based approach to identify strategies that will have the greatest impact on reducing foodborne listeriosis.

A continuum of risk is observed in the human population for listeriosis, ranging from exquisitely sensitive groups, who are highly immunocompromised and at very high risk of listeriosis, through the normal healthy population under 65 years of age, who appear to have a minimal risk for listeriosis.

In addition, unique subpopulations may exist; for example, pregnant Latina women appear to have a higher risk of listeriosis than pregnant women of other races, most likely due to consumption of contaminated soft cheeses such as queso fresco and queso blanco. Certain foods were described as “high risk” for listeriosis. High-risk foods have all of the following properties:

1. have the potential for contamination with L. monocytogenes;
2. support the growth of L. monocytogenes to high numbers
3. are ready-to-eat;
4. require refrigeration; and
5. are stored for an extended period of time.

Control strategies are needed at all stages from pre-harvest to consumption to minimize the likelihood that food will become contaminated by L. monocytogenes and to prevent the growth of the organism to high numbers.

Three main strategies were identified by the Expert Panel for ensuring continuous improvement in reducing foodborne listeriosis:

1. preventing contamination of foods with L. monocytogenes;
2. preventing growth of L. monocytogenes to high numbers in foods; and
3. science-based education messages targeted to susceptible populations and their caregivers.

Of these, the Expert Panel concluded that preventing growth of L. monocytogenes to high numbers would have the greatest impact in reducing cases of listeriosis. Dose-response models predict that the risk of listeriosis increases as the number of organisms in a food increases and can be used as a scientific basis for a target level, below which the organism should be reduced to minimize the likelihood of listeriosis in high-risk populations. This requires implementation of effective food safety control measures and ensuring that they are consistently met. Most effective strategies to control L. monocytogenes in high-risk foods include:

1. Good Manufacturing Practices, sanitation standard operating procedures and HACCP programs, to minimize environmental L. monocytogenes contamination and to prevent cross-contamination in processing plants and at retail;
2. an intensive environmental sampling program in processing plants along with an effective corrective action plan to reduce the likelihood of contamination of high risk foods;
3. time and temperature controls throughout the entire distribution and storage period including establishing acceptable storage times of foods that support growth of L. monocytogenes to high numbers;
4. reformulating foods to prevent or retard the growth of L. monocytogenes, and
5. using post-packaging treatments to destroy L. monocytogenes on products.

Science-based education and risk communication strategies aimed at susceptible populations and focused on high-risk foods should be delivered through health care providers or other credible sources of information. Exquisitely sensitive consumers may become ill when exposed to low numbers of L. monocytogenes or other opportunistic pathogens so reducing the risk to this population could be achieved by maintaining them on restricted low microbial diets during those periods when they are most severely immunocompromised.

Highrisk individuals (i.e., the elderly, pregnant women and most of the immunocompromised) should be provided with guidance on healthy eating, including specific information on high-risk foods that they should avoid, and strategies to reduce their risk, such as thorough cooking, avoidance of cross-contamination, and short-term refrigerated storage of cooked perishable foods. Those at low risk for listeriosis should receive information on safe food handling practices, preferably starting at a pre-school age.

Pages: 30

Published: 2004

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