Role of Foods in Sporadic Listeriosis

Abstract

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<.001). Multivariate analysis showed that of the food specimens that grewL monocytogenes, foods that were ready-to-eat, foods that grewL monocytogenesby a direct-plating method (a measure of the level of contamination), and foods that contained serotype 4b isolates were independently associated with an increased likelihood of containing the patient-matching strain. 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)