Survey of Listeria monocytogenes in ready-to-eat foods

• Published in: Journal of food protection Vol. 66; no. 4; pp. 559 - 569
• Main Authors: Gombas, D.E, Chen, Y, Clavero, R.S, Scott, V.N
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association of Milk, Food and Environmental Sanitarians 01.04.2003
• Subjects: Animals; bacterial contamination; Biological and medical sciences; California; Catering and ready-to-eat meal industries; Colony Count, Microbial; Consumer Product Safety; consumer protection; Dairy Products - microbiology; DNA, Bacterial - isolation & purification; Fish Products - microbiology; food contamination; Food industries; Food Microbiology; Food Packaging; food pathogens; FoodNet (CDC); foodnet sites; Fundamental and applied biological sciences. Psychology; Humans; Lactuca - microbiology; Listeria monocytogenes; Listeria monocytogenes - growth & development; Listeria monocytogenes - isolation & purification; listeriosis; Maryland; Meat Products - microbiology; microbial detection; national surveys; plate count; Prevalence; quantitative analysis; ready-to-eat foods; risk factors; seasonal variation; Seasons; Maryland; California; United States; North America; America; Ready to eat meal; Prevalence; Microbiological testing; Surveillance; Quality control; Listeria monocytogenes; Bacteria; Risk analysis; Biological contamination; Enumeration(counting)
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-66.4.559

The purpose of this study was to develop data on the risk of listeriosis to support a science-based strategy for addressing Listeria monocytogenes in foods in the United States. Eight categories of ready-to-eat foods were collected over 14 to 23 months from retail markets at Maryland and northern California FoodNet sites. The product categories included luncheon meats, deli salads, fresh soft "Hispanic-style" cheeses, bagged salads, blue-veined and soft mold-ripened cheeses, smoked seafood, and seafood salads. The presence and levels of L. monocytogenes in the samples were determined by rapid DNA-based assays in combination with culture methods. Of 31,705 samples tested, 577 were positive. The overall prevalence was 1.82%. with prevalences ranging from 0.17 to 4.7% among the product categories. L. monocytogenes levels in the positive samples varied from <0.3 MPN (most probable number) per g to 1.5 x 10(5) CFU/g, with 402 samples having levels of <0.3 MPN/g, 21 samples having levels of >10(2) CFU/g, and the rest of the samples having intermediate levels. No obvious trends with respect to seasonality were observed. Significant differences (P < 0.05) between the sampling sites were found, with higher prevalences for threes categories in northern California and for two categories in Maryland. Significantly (P < 0.001) higher prevalences were found for in-store-packaged samples than for manufacturer-packaged samples of luncheon meats, deli salads, and seafood salads, while 16 of the 21 samples with higher counts were manufacturer packaged. The data collected in this study help to fill gaps in the knowledge about the occurrence of L. monocytogenes in foods, and this new information should be useful in the assessment of the risk posed by L. monocytogenes to consumers.