Methods to be Reviewed by OMB in 2016

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442 Crowley et al.: Journal of AOAC International Vol. 97, No. 2, 2014
Evaluation of VIDAS® Listeria monocytogenes Xpress (LMX)
for the Detection of Listeria monocytogenes in a Variety of
Foods: First Action 2013.11
Erin C rowley, Patrick Bird, Jonathan Flannery, M. Joseph Benzinger, Jr, Kiel Fisher, Megan Boyle,
Travis H uffman, B en Bastin, Paige Bedinghaus, W illiam Judd, T hao Hoang, James Agin, and David Goins
Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214
Ronald L. Johnson1
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
1Corresponding author’s e-mail:
Supplemental data is available on the J. AOAC Int. website, http://
and follow link
to supplemental data.
DOI: 10.5740/jaoacint.13-368
FOOD BIOLOGICAL CONTAMINANTS
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)
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
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.
Listeria 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
Candidates for 2016 Method of the Year
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