4. AOACRIMicroMethods-2018Awards

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442  C rowley et al . : J ournal of AOAC I nternational V ol . 97, N o . 2, 2014

FOOD BIOLOGICAL CONTAMINANTS

Evaluation of VIDAS ® Listeria monocytogenes Xpress (LMX) for the Detection of Listeria monocytogenes in a Variety of Foods: First Action 2013.11 E rin C rowley , P atrick B ird , J onathan F lannery , M. J oseph B enzinger , J r , K iel F isher , M egan B oyle , T ravis H uffman , B en B astin , P aige B edinghaus , W illiam J udd , T hao H oang , J ames A gin , and D avid G oins Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214 R onald L. J ohnson 1 bioMérieux, Inc., 595 Anglum Rd, Hazelwood, MO 63042 Collaborators: J. Adams; A. Bollenbacher; B. Brahmanda; R. Burkhart; J. Cannon; A. Capps; L. Cesanas-Tyson; D. Davis; D. Ebbing; H. Elgaali; B. Hand; R. Hiles; J. Hirsch; B. Howard; J. Jolly; S. Joseph; A. Kehres; K. Klemms; J. Li; B. May; M. Michels; J. Mills; S. Moore; N. Nagassar; S. Owusu; N. Palen; L. Parker; B. Paul; B. Perry; J. Pickett; N. Rogman; G. Rosario; P. Rule; C. Said; M. Sala-Rhatigan; A. Stegmann; T. Stubblefield; K. Wiggins; J. Zimmerman

Submitted for publication October 31, 2013. The method was approved by the Expert Review Panel for Microbiology Methods for Feed and Environmental Surfaces as First Action. The Expert Review Panel for Microbiology Methods for Feed and Environmental Surfaces invites method users to provide feedback on the First Action methods. Feedback from method users will help verify that the methods are fit for purpose and are critical to gaining global recognition and acceptance of the methods. Comments can be sent directly to the corresponding author or methodfeedback@aoac.org. 1  Corresponding author’s e-mail: ron.johnson@biomerieux.com Supplemental data is available on the J. AOAC Int. website, http:// aoac.publisher.ingentaconnect.com/content/aoac/jaoac and follow link to supplemental data. DOI: 10.5740/jaoacint.13-368 values of 0.04, (–0.08, 0.15) and 0.01, (–0.10, 0.13), with 95% confidence intervals, were obtained, respectively, for 25 and 125 g test portions. The range of the confidence intervals for dLPOD values for both the 25 The VIDAS ® Listeria monocytogenes Xpress (LMX) is an automated rapid screening enzyme immunoassay for the detection of Listeria monocytogenes in food products. The VIDAS LMX method was compared in a multi-laboratory collaborative study to AOAC Official Method 993.12 Listeria monocytogenes in Milk and Dairy Products reference method following current AOAC guidelines. A total of 14 laboratories participated, representing government and industry, throughout the United States. One matrix, queso fresco (soft Mexican cheese), was analyzed using two different test portion sizes, 25 and 125 g. Samples representing each portion size were artificially contaminated with L. monocytogenes at three levels: an uninoculated control level [0 colony forming units (CFU)/test portion], a low inoculum level (0.2–2 CFU/test portion), and a high inoculum level (2–5 CFU/test portion). For this evaluation, 1800 unpaired replicate test portions were analyzed by either the VIDAS LMX or AOAC 993.12. Each level was analyzed using the Probability of Detection (POD) statistical model. For the low-level inoculated test portions, difference in collaborator POD (dLPOD)

and 125 g test portions contain the point 0.0 indicating no statistically significant difference in the number of positive samples detected between the VIDAS LMX and the AOAC method. In addition to Oxford Agar (OXA), VIDAS LMX test portions were confirmed using Agar Listeria Ottavani and Agosti (ALOA), a proprietary chromogenic agar for the identification and differentiation of L. monocytogenes and Listeria species. No differences were observed between the two selective agars. The VIDAS LMX method, with the optional ALOA agar confirmation method, was adopted as Official First Action status for the detection of L. monocytogenes in a variety of foods. L isteria monocytogenes is found widespread throughout the environment, having been isolated from soil, vegetation, marine sediments, and water as well as many different types of food products (1). While L. monocytogenes has long been known to cause illness in animals, it has only more recently been identified as the cause of listeriosis in humans (1). Listeriosis, while rare, can be of great concern for the elderly, pregnant women, infants, and the immunocompromised, as the disease can lead to septicemia, meningitis, encephalitis, or death (2, 3). Outbreaks from L. monocytogenes have been linked to such foods as ready-to-eat deli meats, hot dogs, pâtés, dairy products, soft cheese, smoked seafood, raw sprouts, and most recently cantaloupes (4). The VIDAS Listeria monocytogenes Xpress (LMX) assay, an automated enzyme-based assay for the screening of L. monocytogenes in food, provides the ability to rapidly detect the target analyte in only 1 to 2 days, depending on sample size. The VIDAS LMX assay utilizes two proprietary enrichments to detect L. monocytogenes in food products, LMX broth with supplement for 25 g test portions and VIDAS UP Listeria (LPT) broth for 125 g test portions. The smaller test portions require 26–30 h of incubation, while larger test portions require a 24–30 h primary enrichment incubation followed by a secondary enrichment in 10 mL LPT broth for an additional 22–26 h of incubation. For smaller test portion sizes, the new enrichment

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