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The BAX® System Real-Time PCR Assay for
Salmonella
was certified by the AOAC Research Institute in
1
August, 2012 and designated Performance Tested Method
SM
(PTM) #081201 for testing raw ground beef
2
(25 g and 375 g), chicken carcass rinses, cream cheese, fresh bagged lettuce, dry pet food, and stainless
3
steel. The results of the PTM study demonstrated no significant differences for detection of Salmonella
4
these matrices when comparing the BAX® System method to the standard reference culture procedures
5
described in the U.S. Department of Agriculture-Food Safety and Inspection Service Microbiological
6
Laboratory Guidebook (USDA-FSIS MLG) [1], U.S. Food and Drug Administration Bacteriological
7
Analytical Manual (FDA BAM) [2], and Health Canada Compendium of Analytical Methods (HC CAM) [3]
8
(see attachments “BAX RT Salm AOAC PTM Report Final”). After the PTM approval was achieved, a
9
procedure change was applied to this validation to incorporate an eight-cycle increase in processing
10
time in the BAX® System Q7 instrument (see attachment “Modification Report RT Sal plus 8 cycles Final
11
(3)”).
12
Following the completion of the PTM study and procedure change, a pre-collaborative study was
13
conducted on an additional 18 matrices. The results obtained using the test method indicate no
14
statistical difference when compared to the corresponding reference method results.
15
Study Design
16
A pre-collaborative study was conducted in accordance with the AOAC INTERNATIONAL Methods
17
Committee Guidelines for Validation of Microbiological Methods for Food and Environmental Surfaces
18
[4] to evaluate the ability of the DuPont™ BAX® System Real-Time PCR Assay for
Salmonella
to detect
19
the target species in a variety of foods and environmental surfaces. This study was performed by DuPont
20
Nutrition & Health on 18 different sample types to demonstrate the reliability of the test method among
21
a wide variety of sample types. Sample types tested include ground beef with soy, beef trim,
22
frankfurters, shrimp, ground turkey, chicken wings, dried eggs, shell eggs, frozen peas, orange juice,
23
nonfat dry milk, ice cream, peanut butter, cocoa, white pepper, infant formula, ceramic tile, and plastic
24
surfaces.
25
Test Sample Preparation
26
Most sample types evaluated in this study were artificially inoculated with a
Salmonella
strain at levels
27
expected to produce low (0.2–2.0 cfu/test portion) or high (5 cfu/test portion) spike levels on the day of
28
analysis; chicken wings were naturally contaminated. A different
Salmonella
strain was used for each
29
matrix (see Table 1). All artificial inoculation strains were selected from the DuPont Qualicon Culture
30
Collection or the American Type Culture Collection. To artificially contaminate samples, a pure culture of
31
each strain was grown overnight in BHI broth at 35-37°C, then diluted in additional BHI broth to levels
32
expected to produce fractional positive results based on preparatory studies.
Salmonella
strains used to
33
inoculate processed foods were heated in a water bath at 55°C for 10 minutes to subject them to heat
34
injury before spiking test samples.
35
Dupont BAX Salmonella Pre- Collaborative Study
For Expert Review Panel Use Only
Do Not Distribute
AOAC INTERNATIONAL