Comparison between qPCR, VIDAS immunoassays, and agar streaking for the detection of Listeria monocytogenes from food and environmental surfaces containing and not containing Listeria innocua

Zhihan Xian; Jiyoon Yoo; Chadni Patel; Helen Yang; Xiangyu Deng; Thomas Hammack; Yi Chen

Journal of Food Protection (May 2023)

Comparison between qPCR, VIDAS immunoassays, and agar streaking for the detection of Listeria monocytogenes from food and environmental surfaces containing and not containing Listeria innocua

Zhihan Xian,
Jiyoon Yoo,
Chadni Patel,
Helen Yang,
Xiangyu Deng,
Thomas Hammack,
Yi Chen

Affiliations

Zhihan Xian: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740, USA
Jiyoon Yoo: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740, USA
Chadni Patel: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740, USA
Helen Yang: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740, USA
Xiangyu Deng: Department of Food Science, University of Georgia, Griffin, GA 30223, USA
Thomas Hammack: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740, USA
Yi Chen: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740, USA

Journal volume & issue: Vol. 86, no. 5
p. 100013

Abstract

Read online

Comparisons among a qPCR assay, VIDAS® assays and a conventional agar streaking method following the same enrichment for the detection of Listeria monocytogenes were performed under two challenging conditions. In the first comparison, L. innocua and L. monocytogenes were coinoculated into sausages at ratios (L. innocua-to-L. monocytogenes) of 10, 100, 1000, and 10 000. qPCR provided the most sensitive detection at all ratios after both 24-h and 48-h enrichments. A modified VIDAS® LMO2 assay (i.e., replacement of the kit-specified enrichment scheme with the enrichment scheme used in this study) and agar streaking yielded equivalent results when the ratio was 10 and 100; agar streaking was more sensitive when the ratio was 1000; neither method could detect L. monocytogenes at the ratio of 10 000. Enrichment duration of 48 h was needed for modified VIDAS® to detect L. monocytogenes when the ratio was 1000. Agar streaking after 24-h enrichment isolated L. monocytogenes better than after 48-h enrichment when the ratio was 100 and 1000. In the second comparison, we followed the validation guidelines of AOAC International and inoculated L. monocytogenes, without any L. innocua, onto lettuce and stainless-steel surfaces at low levels. The numbers of positive samples detected by qPCR, VIDAS® LIS assay, modified VIDAS® LMO2 assay, and agar streaking after 48-h enrichment were not statistically different. Our data showed that qPCR was the most sensitive method, while agar streaking and VIDAS® performed reasonably well. Streaking after 24-h enrichment was needed when background flora could overgrow L. monocytogenes during prolonged enrichment, and this is critical for confirming rapid screening assays. Appropriate selection of enrichment duration and rapid assays will enhance the testing of L. monocytogenes in food and environmental samples.

Published in Journal of Food Protection

ISSN: 0362-028X (Print); 1944-9097 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Technology: Chemical technology: Food processing and manufacture; Technology: Home economics: Nutrition. Foods and food supply
Website: https://www.sciencedirect.com/journal/journal-of-food-protection

About the journal

Abstract

Keywords