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Evaluation of VIDAS
Listeriamonocytogenes
Xpress (LMX) for the
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Detection of
Listeriamonocytogenes
in a Variety of Foods:
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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, Will Judd, Thao Hoang,James Agin,
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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, J. Adams, A. Bollenbacher, K. Wiggins, L.
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Cesanas, J. Jolly, S. Moore, D. Ebbing, M. Michels, A. Kehres, J. Hirsch
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The VIDAS
®
Listeria monocytogenes
Xpress (LMX) is an automated rapid
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screening enzyme immunoassay for the detection of
Listeria monocytogenes
in
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food products.The VIDAS LMX method was compared in a multi-laboratory
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collaborative study to the AOAC OMA 993.12
Listeria monocytogenes in Milk and
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Dairy Products
reference method following current AOAC Guidelines.A total of 14
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laboratories participated, representing government and industry, throughout the
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United States. One matrix, queso fresco (soft Mexican cheese), was analyzed
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using 2 different test portion sizes, 25 g and 125 g. Each test portion was
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artificially contaminated with
Listeria monocytogenes
at 3 inoculation levels: an
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un-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 LMX 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 0.04, (-0.08, 0.15) and 0.01, (-0.10, 0.13),
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with 95% confidence intervals, were obtained, respectively for 25 g and
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125 g test portions. The range of the confidence intervals for dLPOD values for
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both the 25g and 125g test portions contain the point 0.0 indicating no
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statistically significant difference in the number of positive samples detected
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between the VIDAS LMXand the AOAC methods. In addition to Oxford Agar,
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VIDAS LMX test portions were confirmed using ALOA, a proprietary chromogenic
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agar for the identification and differentiation of
L. monocytogenes
and
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Listeria
species. No differences were observed between the two selective
agars.It41
is recommended that the VIDAS LMX method, with the optional ALOA agar
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confirmation method, be adopted as Official First Action status for the detection
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of
Listeria monocytogenes
in a variety of foods.
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