Role of Foods in Sporadic Listeriosis: II. Microbilogic and Epidemiologic Investigation

Objective. —To evaluate the role of foods in sporadic listeriosis. Design. —Microbiologic survey of foods collected from refrigerators of patients with listeriosis identified through active laboratory-based surveillance. Patient and foodListeria monocytogenesisolates were subtyped to identify foods contaminated with the same strain ofL monocytogenesthat caused illness in the patient; samples of these foods were obtained from the retail source. Setting. —Multistate population-based study conducted between 1988 and 1990. Results. —Listeria monocytogenesgrew from at least one food specimen in the refrigerators of 79 (64%) of 123 listeriosis patients; 11% of more than 2000 food specimens collected in the study containedL monocytogenes. Twenty-six (33%) of 79 refrigerators with foods that grewL monocytogenescontained at least one food isolate of the same strain as that in the corresponding patient, a frequency much higher than would be expected by chance (P Conclusion. —We identified specific food andL monocytogenesisolate characteristics—ready-to-eat foods, foods containing higher concentrations ofL monocytogenes, and foods containing serotype 4b—which were associated with disease-causing strains. These results can provide guidance to industry and regulatory agencies in developing strategies to prevent listeriosis. (JAMA. 1992;267:2046-2050)