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868 Wallace et al.: Journal of AOAC International Vol. 97, N o. 3, 2014
Detection of Salmonella species in a Variety of Foods by the
DuPont™ BAX® System Real-Time PCRAssay for Salmonella:
First Action 2013.02
F. Morgan Wallace , Bridget Andaloro, Dawn Fallon, Nisha Corrigan, Stephen Varkey,
Daniel DeMarco, Andrew Farnum, Monica Tadler, Steven H oelzer, Julie Weller, Eugene Davis,
Jeffrey Rohrbeck, and George Tice
DuPont Nutrition & Health, ESL Building 400, Route 141 and Henry Clay Rd, Wilmington, DE 19880
Patrick Bird , Erin Crowley, Jonathan Flannery, Kiel Fisher, T ravis Huffman, Megan Boyle,
M. Joseph Benzinger, Jr, Paige Bedinghaus, Katie G oetz, William Judd, J im Agin, and David Goins
Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214
Collaborators: C. Churchill; D. Clark, Jr; B. Dieckelman; T. Donohue; H. Elgaali; W. Fedio; E. Galbraith; L. Hahn; D. Kondratko;
B. Kupski; K. McCallum; G. McWhorter; J. Meyer; J. Putrow; R. Radcliff; D. Rodgers; S. Scott; D. Swift; L. Thompson
Received December 13, 2013.
The method was approved by the Expert Review Panel for Food
Biological Contaminants as First Action.
The Expert Review Panel for Food Biological Contaminants
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
Corresponding author’s e-mail:
Appendices are available on the J. AOAC Int. website, http://aoac.
DOI: 10.5740/jaoacint.13-407
FOOD BIOLOGICAL CONTAMINANTS
A multilaboratory study was conducted to
evaluate the ability of the DuPont™ BAX® System
Real-Time PCR Assay for Salmonella to detect the
target species in a variety of foods and environmental
surfaces. Internal validation studies were performed
by DuPont Nutrition & Health on 24 different sample
types to demonstrate the reliability of the test
method among a wide variety of sample types. Two
of these matrixes—pork and turkey frankfurters
and pasteurized, not-from-concentrate orange juice
without pulp—were each evaluated in 14 independent
laboratories as part of the collaborative study to
demonstrate repeatability and reproducibility of the
internal laboratory results independent of the end
user. Frankfurter samples were evaluated against
the U.S. Department of Agriculture, Food Safety and
Inspection Service reference method as a paired
study, while orange juice samples were evaluated
against the U.S. Food and Drug Administration
reference method as an unpaired study, using a
proprietary media for the test method. Samples
tested in this study were artificially inoculated with a
Salmonella strain at levels expected to produce low
(0.2–2.0 CFU/test portion) or high (5 CFU/test portion)
spike levels on the day of analysis. For each matrix,
the collaborative study failed to show a statistically
significant difference between the candidate method
and the reference method using the probability of
detection statistical model.
Salmonella is a leading cause of foodborne illness. The
low infectious dose of the bacterium makes it critical
to detect even low concentrations of the Salmonella in
foods. Additionally, the presence of high concentrations of
closely related nonpathogenic bacteria create the need for highly
accurate methodologies. Traditionally, laboratories concerned
with detection of Salmonella screened food samples with culture
methods, such as those provided by the U.S. Department of
Agriculture, Food Safety and Inspection Service (USDA-FSIS)
and the U.S. Food and Drug Administration (FDA), which
require several days to detect and confirm Salmonella. Rapid
methods of screening for Salmonella have been developed, but
these generally require 2 days of enrichment. By contrast, the
DuPont™ BAX® System detects the pathogen less than 90 min
after enrichment, and the DNA-based results are both reliable
and reproducible, leading to quicker release of cleared product.
The BAX System Real-Time PCR Assay for Salmonella
was certified by the AOAC Research Institute in August
2012 and designated Performance Tested MethodSM (PTM)
No. 081201. No significant differences were reported
for detection of Salmonella in the matrixes tested when
comparing the BAX System method results to the standard
reference culture procedures described in the USDA-FSIS
Microbiology Laboratory Guidebook (MLG; 1), FDA
Bacteriological Analytical Manual (BAM; 2), and Health
Canada Compendium of Analytical Methods (HC CAM; 3).
The matrixes validated in the PTM study included raw
ground beef (85% lean, 25 and 375 g), chicken carcass rinse,
cream cheese (34% fat), fresh bagged lettuce, dry pet food,
and stainless steel. Inclusivity testing demonstrated that the
BAX System method was reactive with 317 Salmonella
isolates, representing over 100 different serotypes. The test
method did not detect 37 different non-Salmonella strains
tested (Appendix 1; see appendixes on J. AOAC Int. website,
).
After the PTM approval was achieved, a procedure change
was applied to this validation to incorporate an eight-cycle
increase in processing time in the BAX System Q7 instrument
(Appendix 2).
Following the completion of the PTMstudy, a precollaborative
study was conducted on an additional 18 matrixes, including
Candidates for 2016 Method of the Year
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