Journal of Food Protection, Vol. 80, No. 6, 2017, Pages 903–921
doi:10.4315/0362-028X.JFP-16-420
JOHN B. LUCHANSKY¹, YUHUAN CHEN², ANNA C. S. PORTO-FETT¹, REGIS POUILLOT², BRADLEY A. SHOYER¹,RACHEL JOHNSON-DERYCKE³, DENISE R. EBLEN³, KARIN HOELZER², WILLIAM K. SHAW, JR.³, JANE M. VAN DOREN², MICHELLE CATLIN³, JEEHYUN LEE⁴, ROHAN TIKEKAR⁴, DANIEL GALLAGHER⁵, JAMES A. LINDSAY¹, THE LISTERIA MARKET BASKET SURVEY MULTI-INSTITUTIONAL TEAM, AND SHERRI DENNIS^2
1U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038.
²U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Drive, College Park, Maryland 20740.
³ U.S. Department of Agriculture, Food Safety and Inspection Service, Patriots Plaza III, 1400 Independence Avenue SW, Washington, D.C. 20250.
⁴ Department of Food Science, Drexel University, 101 North 33rd Street, Philadelphia, Pennsylvania 19104.
⁵ Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, 409 Durham Hall, Blacksburg, Virginia 24061, USA.

Abstract

A multiyear interagency Listeria monocytogenes Market Basket Survey was undertaken for selected refrigerated ready-to-eat foods purchased at retail in four FoodNet sites in the United States. Food samples from 16 food categories in six broad groups (seafood, produce, dairy, meat, eggs, and combination foods) were collected weekly at large national chain supermarkets and independent grocery stores in California, Maryland, Connecticut, and Georgia for 100 weeks between December 2010 and March 2013. Of the 27,389 total samples, 116 samples tested positive by the BAX PCR system for L. monocytogenes , and the pathogen was isolated and confirmed for 102 samples. Among the 16 food categories, the proportion of positive samples (i.e., without considering clustering effects) based on recovery of a viable isolate of L. monocytogenes ranged from 0.00% (95% confidence interval: 0.00, 0.18) for the category of soft-ripened and semisoft cheese to 1.07% (0.63, 1.68) for raw cut vegetables. Among the 571 samples that tested positive for Listeria-like organisms, the proportion of positive samples ranged from 0.79% (0.45, 1.28) for soft-ripened and semisoft cheese to 4.76% (2.80, 7.51) for fresh crab meat or sushi. Across all 16 categories, L. monocytogenes contamination was significantly associated with the four states (P < 0.05) but not with the packaging location (prepackaged by the manufacturer versus made and/or packaged in the store), the type of store (national chain versus independent), or the season. Among the 102 samples positive for L. monocytogenes , levels ranged from <0.036 most probable number per g to 6.1 log CFU/g. For delicatessen (deli) meats, smoked seafood, seafood salads, soft-ripened and semisoft cheeses, and deli-type salads without meat, the percentage of positive samples was significantly lower (P < 0.001) in this survey than that reported a decade ago based on comparable surveys in the United States. Use of mixed logistic regression models to address clustering effects with regard to the stores revealed that L. monocytogenes prevalence ranged from 0.11% (0.03, 0.34) for sprouts (prepackaged) to 1.01% (0.58, 1.74) for raw cut vegetables (prepackaged).