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DuPont™ BAX
®
System Real-Time PCR Assay for
Salmonella
: Collaborative Study
DuPont Nutrition & Health
Page 2
Introduction
1
Salmonella
is a leading cause of foodborne illness. The low infectious dose of the bacterium makes it
2
critical to detect even low concentrations of the
Salmonella
in foods. Additionally, the presence of high
3
concentrations of closely related non-pathogenic bacteria create the need for highly accurate
4
methodologies. Traditionally, labs concerned with detection of
Salmonella
screened food samples with
5
culture methods, such as those provided by the United States Department of Agriculture Food Safety
6
and Inspection Service (USDA-FSIS) and the U. S. Food and Drug Administration’s (FDA), which require
7
several days to detect and confirm
Salmonella
. Rapid methods of screening for
Salmonella
have been
8
developed, but these generally require two days of enrichment. By contrast, the DuPont™ BAX® System
9
detects the pathogen less than 90 minutes after enrichment, and the DNA-based results are both
10
reliable and reproducible, leading to quicker release of cleared product.
11
The BAX® System Real-Time PCR Assay for
Salmonella
was certified by the AOAC Research Institute in
12
August, 2012 and designated Performance Tested Method
SM
(PTM) #081201. No significant differences
13
were reported for detection of
Salmonella
in the matrices tested when comparing the BAX® System
14
method results to the standard reference culture procedures described in the U.S. Department of
15
Agriculture-Food Safety and Inspection Service Microbiological Laboratory Guidebook (USDA-FSIS MLG)
16
[1], U.S. Food and Drug Administration Bacteriological Analytical Manual (FDA BAM) [2], and Health
17
Canada Compendium of Analytical Methods (HC CAM) [3]. The matrices validated in the PTM study
18
included raw ground beef (85% lean, 25 g and 375 g), chicken carcass rinse, cream cheese, fresh bagged
19
lettuce, dry pet food, and stainless steel. Inclusivity testing demonstrated that the BAX® System method
20
was reactive with 317
Salmonella
isolates, representing over 100 different serotypes. The test method
21
did not detect 37 different non-
Salmonella
strains tested.
22
Following the completion of the PTM study, a pre-collaborative study was conducted on an additional 18
23
matrices, including ground beef with soy (85% lean), beef trim, frankfurters (beef), shrimp, ground
24
turkey, chicken wings, dried eggs (whole, powdered), shell eggs, frozen peas, orange juice, instant
25
nonfat dry milk, ice cream (12% fat), peanut butter, cocoa (unsweetened), white pepper, milk-based
26
infant formula, ceramic tile, and plastic surfaces. The results obtained using the test method indicate no
27
statistical difference with the reference method when compared to the corresponding reference
28
method results.
29
In addition, two of the pre-collaborative study matrices – frankfurters (pork plus turkey) and orange
30
juice(pasteurized not-from-concentrate) – were evaluated in a total of 15 independent laboratories as
31
part of the collaborative study to demonstrate repeatability of the internal laboratory results
32
independent of the end user. The results obtained using the test method indicate no statistical
33
difference when compared to the corresponding reference method results.
34
Study Design
35
Collaborators analyzed 2 representative matrices (pork and turkey frankfurters and pasteurized, not-
36
from-concentrate orange juice without pulp) at 3 contamination levels (low, high and un-inoculated)
37
comparing the performance of the BAX® System Real-Time PCR Assay for
Salmonella
to appropriate
38
FINAL (Version 4)