Listeria Risk Assessment
Richard C. Whiting, Food and Drug Administration, Center for Food Safety and Applied Nutrition, Washington, D.C. 20204
Listeria monocytogenes is a bacterium widely found in soils, water and food processing plants. Consequently, it is frequently found in our foods, usually in low numbers. For most people this bacterium is harmless but for individuals with impaired immune systems from diseases, medical treatments and old age, it can cause systemic infections and meningitis (listeriosis). Pregnant women and neonates are also highly susceptible to listeriosis. The rate of infection from Listeria is relatively low compared to other food borne pathogens, however, death results in 20% of the cases. Epidemiological investigations are hampered by the sporadic occurrences of listeriosis and the two to three weeks or longer between consumption of the food and onset of illness. Based upon a qualitative evaluation of this information, governments have implemented different degrees of stringency in the tolerance of this microorganism in foods, particularly ready-to-eat foods that are eaten without cooking immediately prior to consumption. This risk assessment collected all of the relevant scientific information and constructed a quantitative description of the sources of Listeria in our diet and the health risk of consuming particular numbers of Listeria. In addition to describing what is known, the risk assessment provided an assessment of the quality of this information and highlighted where crucial information is lacking. This approach provides regulatory agencies with a more comprehensive and integrated description of this public health hazard than the more qualitative and subjective interpretation done previously, thereby leading to more informed decisions.