Enumeration and characterization of Listeria monocytogenes in novelty ice cream samples manufactured on a specific production line linked to a listeriosis outbreak |
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| Affiliation: | 1. Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, 8301 Muirkirk Rd, Laurel, MD 20708, USA;2. Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, 5001 Campus Dr., College Park, MD 20740, USA;1. Department of Agricultural and Food Sciences, Alma Mater Studiorum, University of Bologna, Campus of Food Science, Piazza Goidanich 60, 47521 Cesena, Italy;2. Interdepartmental Center for Industrial Agri-food Research, University of Bologna, Piazza Goidanich 60, 47521 Cesena (FC), Italy;1. INBIONATEC, CONICET, Universidad Nacional de Santiago del Estero, RN 9, Km 1125, 4206 Santiago del Estero, Argentina;2. CIQA, CONICET, Departamento de Ingeniería Química, Facultad Regional Córdoba, Universidad Tecnológica Nacional, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba, Argentina;3. Centro de Investigaciones en Biofísica Aplicada y Alimentos (CIBAAL), CONICET, Universidad Nacional de Santiago del Estero, RN 9, Km 1125, 4206 Santiago del Estero, Argentina;4. Laboratorio de Microbiología Molecular, Instituto de Microbiología Básica y Aplicada, Universidad Nacional de Quilmes, Roque Saenz Peña 352, B1876BXD Bernal, Argentina;1. Center for Food Safety and Applied Nutrition, Food and Drug Administration, United States;2. Office of Regulatory Affairs, Food and Drug Administration, United States |
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| Abstract: | Listeriosis is an invasive illness typically caused by the ingestion of foods contaminated with Listeria monocytogenes. In 2015, an outbreak of listeriosis was linked to ice cream products produced on a specific production line at Facility X. The United States Food and Drug Administration (FDA) obtained samples representing several lots of three products manufactured on that line from May 2014 through January 2015. Two of these products, A and B, while not linked to any reported illnesses, were analyzed to determine the frequency of contamination and the contamination level for risk assessment and dose-response analyses. These enumerations were performed utilizing a Most Probable Number (MPN) method, with a lower detection limit of 0.03 MPN/g, on 344 samples of Product A and 95 samples of Product B. Ten lots of Product A were analyzed and 77% of the samples tested were found to be positive for L. monocytogenes. Five lots of Product B were analyzed and 46% of the tested samples were found to be positive. Additionally, the level of contamination of positive Product B samples was always less than 1 MPN/g. The contamination levels of both products, overall, were low with median values of 0.1 MPN/g and 0.02 MPN/g for Products A and B, respectively. A majority of Product A samples (52%) were contaminated at levels of less than 1 MPN/g and only one sample was above 100 MPN/g. Whole genome sequencing (WGS) of L. monocytogenes isolated from ice cream samples produced in the line suggested minor strain differences related to product type, possibly due to differences in the food matrices and/or differences in the manufacturing equipment. Overall, the data showed a consistent low level of contamination in products produced from a single production line over a nine month period. |
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| Keywords: | Listeriosis Ice cream Enumeration Whole genome sequencing |
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