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ournal of
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. 3, 2014
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observed for each matrix collaboratively studied, the S
L
value
(between-laboratory effect components of S
R
) being zero
in both data sets at each partial response spike level. This
acceptable interlaboratory reproducibility is supported by the
insignificant homogeneity test P
T
values (>0.1), which suggest
that the laboratory POD values are not significantly different
when allowance is made for the sampling variability. While
interpretation of this latter test is subject to the study design, 10
or more laboratories with 12 replicate sample portions per level
for each of three levels (high, low, and unspiked) per laboratory
is deemed adequate for such studies.
The graphical representation of the data (Appendix 4,
Figure 1) demonstrates that the dose-response curve for each
matrix encompasses the partial response region required for
qualitative detection method analysis. The 95% confidence
interval of each dPOD value determined at each concentration
contains zero, which is indicative of no significant difference
between the candidate and reference methods and between the
candidate presumptive result and candidate confirmed result.
Conclusions
Within the statistical constraints of these studies, no
differences were found between the reference culture-based
methods and the alternative BAX System method. These
results indicate that the alternative method can be used to
allow uncontaminated food to be released rapidly from a
manufacturer’s control and prevents
Salmonella
-contaminated
foods from entering commerce. Furthermore, this test method
can be a valuable tool for outbreak investigations when food
contamination events occur.
Collaborator feedback indicated that the method was easy
to use and that the clear yes/no results provided by the BAX
System software were appreciated. Time and labor savings were
cited as key advantages of the test method over the reference
culture methods. No negative feedback regarding the method
was provided by any of the collaborators.
The DuPont BAX System Real-Time PCR Assay for
Salmonella
was adopted as Official First Action status for the
detection of
Salmonella
in a variety of foods, including raw
ground beef, ground beef with soy, beef trim, frankfurters,
shrimp, ground turkey, chicken wings, poultry rinse, dried
eggs, shell eggs, fresh bagged lettuce, frozen peas, orange juice,
cream cheese, nonfat dry milk, ice cream, peanut butter, cocoa,
white pepper, infant formula, and dry pet food, and on stainless
steel, ceramic tile, and plastic surfaces.
Acknowledgments
We sincerely thank the following collaborators for their
dedicated participation in this study:
Bryan Dieckelman, Deibel Laboratories (Lincolnwood, IL)
Tom Donohue, LeAnne Hahn, and Catherine Churchill,
Deibel Laboratories (Madison, WI)
Hesham Elgaali, Indiana Department of Health (Indianapolis,
IN)
Willis Fedio, New Mexico State University (Las Cruces,
NM)
Elizabeth Galbraith, DuPont Nutrition & Health (Waukesha,
WI)
Brian Kupski, Silliker Laboratories (Crete, IL)
Kristina McCallum and Dominika Kondratko, Colorado
Department of Agriculture (Denver, CO)
Guy McWhorter, ABC Research Laboratories (Gainesville,
FL)
Joe Meyer and Demi Swift, Covance Laboratories (Monona,
WI)
Roy Radcliff and Dorn Clark, Jr, Marshfield Food Safety
(Marshfield, WI)
Dora Rodgers, Samantha Scott, and Joseph Putrow,Wisconsin
Department of Agriculture (Madison, WI)
Leslie Thompson, AEGIS FOOD TESTING Laboratories
(North Sioux City, SD)
We would also like to thank Nicolette Blubaugh (DuPont
Nutrition & Health, Wilmington, DE) for invaluable assistance
in the preparation of this manuscript and Maria Nelson (AOAC
INTERNATIONAL, Gaithersburg, MD) for her expertise and
assistance in the design and execution of this study.
References
(1) U.S. Department of Agriculture-Food Safety and Inspection
Service (2011)
Microbiology Laboratory Guidebook,
Chapter
4.05, Isolation and Identification of
Salmonella
from Meat,
Poultry, Pasteurized Egg and Catfish Products,
http://www.fsis.
usda.gov/PDF/MLG_4_05.pdf
(2) U.S. Food and Drug Administration (2011)
Bacteriological
Analytical Manual
, Chapter 5,
Salmonella
,
http://www.fda.gov/food/foodscienceresearch/laboratorymethods/ucm070149
(3) Reid, A. (2009) MFHPB-20, Isolation and Identification of
Salmonella
from Food and Environmental Samples. In: Health
Canada Compendium, Vol. 3, Laboratory Procedures for the
Microbiological Examination of Foods, Health Canada, Health
Products and Food Branch,
http://www.hc-sc.gc.ca/fn-an/res-rech/analy-meth/microbio/volume2/mfhpb20-01-eng.php
(4)
Official Methods of Analysis
(2012) 19th Ed., AOAC
INTERNATIONAL, Gaithersburg, MD, Appendix J:
AOAC INTERNATIONAL Methods Committee Guidelines
for Validation of Microbiological Methods for Food and
Environmental Surfaces,
www.eoma.aoac.org/app_j.pdf(5) Least Cost Formulations, Ltd, MPN Calculator-Version 1.6,
http://www.lcfltd.com/customer/LCFMPNCalculator.exe(6) Least Cost Formulations, Ltd (2011) AOAC Binary Data
Interlaboratory Study Workbook,
http://lcfltd.com/aoac/aoac-binary-v2-2.xls
Candidates for 2016 Method of the Year
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