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Evaluation of VIDAS
UP
Listeria
assay (LPT) for the Detection of
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Listeria
in a Variety of Foods and Environmental Surfaces:
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Collaborative Study
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Erin Crowley, Patrick Bird,Jonathan Flannery,M. Joseph Benzinger, Jr., Kiel Fisher, Megan
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Boyle, Travis Huffman,Ben Bastin, Paige Bedinghaus, WilliamJudd, Thao Hoang,
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James Agin, David Goins
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Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214
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Ronald L. Johnson
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bioMérieux, Inc., 595 Anglum Rd, Hazelwood, MO 63042
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Collaborators: J. Mills, P. Rule, B. Howard, N. Rogman, J. Cannon, B. Paul,M. Sala-Rhatigan, S.
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Josephs, N. Palen,A. Stegmann, B. Perry, R. Hiles,T. Stubblefield, N. Nagassar,Sylvanus Owusu , J.
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Zimmerman, B. Brahmanda, H. Elgaali, A. Capps, G. Rosario, D. Davis, L. Parker, C. Said, J. Li, K.
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Klemms, B. May, B. Hand, R. Burkhart, J. Pickett, , A. Bollenbacher, K. Wiggins, L. Cesanas, J.
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Jolly, S. Moore, D. Ebbing, M. Michels, A. Kehres, J. Hirsch
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The VIDAS
®
UP
Listeria
(LPT) is an automated rapid screening enzyme phage-
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ligand based assay for the detection of
Listeria
speciesin human food products
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and environmental samples. The VIDAS LPT method was compared in a multi-
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laboratory collaborative study to the AOAC OMA 993.12
Listeria monocytogenes
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in Milk and Dairy Products
reference method following current AOAC
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Guidelines.A total of 14 laboratories participated,representing governmentand
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industry, throughout the United States. One matrix, queso fresco (soft Mexican
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cheese), was analyzed using 2 different test portion sizes, 25 g and 125 g. Each
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test portion was artificially contaminated with
Listeria
species at 3 levels, an un-
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inoculated control level (0 colony forming units (CFU)/test portion), a low
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inoculum level (0.2-2 CFU/test portion) and a high inoculum level (2-5 CFU/test
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portion). For this evaluation, 1,800unpaired replicate test portions were analyzed
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by either the VIDAS LPT or AOAC method. Each inoculation level was analyzed
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using the Probability of Detection (POD) statistical model. For the low level
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inoculated test portions, dLPOD values of 0.01, (-0.10, 0.13), with 95% confidence
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intervals, were obtained for both 25 g and 125 g test portions.The range of the
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confidence intervals for dLPOD values for both the 25g and 125g test portions
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contain the point 0.0 indicating no statistically significant difference in the
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number of positive samples detected between the VIDAS LPT and the AOAC
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methods. In addition to Oxford agar, VIDAS LPT test portions were confirmed
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using ALOA, a proprietary chromogenic agarfor the identification and
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differentiation of
L. monocytogenes
and
L.
species. No differences were
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observed between the two selective agars. It is recommended that the VIDAS
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LPT method, with the optional ALOA agar confirmation method, be adopted as
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Official First Action status for the detection of
Listeria
species in a variety of
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foods and environmental samples.
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