America's Center - St. Louis
Laurel Burall, U.S. Food and Drug Administration-CFSAN, Laurel, MD
Yi Chen, U.S. Food and Drug Administration-CFSAN, College Park, MD
Dumitru Macarisin, U.S. Food and Drug Administration-CFSAN, College Park, MD
Regis Pouillot, U.S. Food and Drug Administration-CFSAN, College Park, MD
Errol Strain, U.S. Food and Drug Administration-CFSAN, College Park, MD
Antonio J. De Jesús, U.S. Food and Drug Administration-CFSAN, College Park, MD
Anna Laasri, U.S. Food and Drug Administration-CFSAN, College Park, MD
Hua Wang, U.S. Food and Drug Administration-CFSAN, College Park, MD
Laila Ali, U.S. Food and Drug Administration, College Park, MD
Aparna Tatavarthy, U.S. Food and Drug Administration, College Park, MD
Guodong Zhang, U.S. Food and Drug Administration-CFSAN, College Park, MD
Lijun Hu, U.S. Food and Drug Administration, College Park, MD
James Day, U.S. Food and Drug Administration-CFSAN, College Park, MD
Jihun Kang, U.S. Food and Drug Administration-CFSAN, Laurel, MD
Surasri Sahu, U.S. Food and Drug Administration-CFSAN, Laurel, MD
Devayani Srinivasan, U.S. Food and Drug Administration-CFSAN, Laurel, MD
Mickey Parish, U.S. Food and Drug Administration-CFSAN, College Park, MD
Peter Evans, U.S. Food and Drug Administration-CFSAN, College Park, MD
Eric Brown, U.S. Food and Drug Administration-CFSAN, College Park, MD
Thomas Hammack, U.S. Food and Drug Administration, College Park, MD
Donald Zink, IEH Laboratories & Consulting Group, Lake Forest Park, WA
Atin Datta, U.S. Food and Drug Administration-CFSAN, Laurel, MD
Introduction: Listeriosis is an invasive illness typically caused by the ingestion of food products contaminated with
L. monocytogenes. An outbreak of listeriosis in 2015 was linked to ice cream produced at plants in two different states linked to the same firm. One of the implicated products, Product C, was produced on a specific production line at one plant. The FDA was able to obtain and enumerate samples representing several lots of three of the Products, A, B and C, made on that line. Product C, linked to illness, was evaluated separately.
Purpose: Two products, A and B, not linked to illness, were enumerated in this study via a most probable number (MPN) method to determine their contamination level for future risk assessment and dose-response analyses.
Methods: An MPN scheme with a detection limit of 0.03 MPN/g was used to analyze 344 samples of Product A from ten lots and 95 samples of Product B, representing five lots. These products encompass production dates spanning a nine-month period.
Results: A total of 76% of Product A samples were positive for L. monocytogenes while 46% of Product B were positive. Additionally, the contamination level was less in Product B than Product A (median of 0.02 MPN/g and 0.1 MPN/g, respectively). All positive Product B samples had L. monocytogenes at levels of less than 1 MPN/g. Product A contamination levels were predominantly less than 1 MPN/g (52%) with the remaining 24% mostly between 1 to 50 MPN/g, with only one sample above 100 MPN/g.
Significance: These enumeration data show the extent and variability in contamination levels of L. monocytogenes in these ice cream products manufactured on a contaminated line. These data, combined with the epidemiological data, will improve our understanding of the contamination patterns, as well as dose response and risk assessment.
