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during test portion preparation at the coordinating laboratory is not believed to be the cause of
1
the positive control samples.
2
During the analysis of both the raw ground beef and wet pet food, some laboratories produced
3
false positive results with the candidate method. The 3M Molecular Detection Assay is intended
4
for use in a laboratory environment by professionals trained in laboratory technique. Cross
5
contamination of samples resulting in false positive results may occur if careful molecular
6
techniques are not followed. To reduce the risk of cross contamination, 3M recommends the use
7
of sterile, aerosol barrier (filtered) molecular biology grade pipette tips. A new pipette tip should
8
be used for each sample transfer, and the user may choose to add an intermediate transfer step in
9
order to avoid pipette contamination, i.e. each enriched sample can be transferred into a sterile
10
tube before proceeding into the lysis step. Discrepant results may be obtained if deviations from
11
the method occur. Use of calibrated pipettors and thermometers is critical to ensure that correct
12
volumes of samples, especially when hydrating the Reagent tubes, and appropriate temperatures
13
are utilized. It is recommended that users read and become familiar with the 3M Molecular
14
Detection Assay Salmonella Product Instructions and follow them carefully. .
15
For either matrix, the collaborative study failed to show a statistically significant difference
16
between the candidate method and the reference method using the POD model when the
17
aforementioned four laboratories were removed from consideration.
18
19
Recommendations
20
21
It is recommended that the 3M Molecular Detection Assay
Salmonella
method be adopted as
22
Official First Action status for the detection of
Salmonella
in selected foods including raw
23
ground beef (25 g, 325 g, 375 g), raw ground chicken (25 g, 325 g), cooked breaded chicken
24
(325 g), pasteurized liquid whole egg (100 g), raw shrimp (head-off, 25 g), fresh spinach
25
(bagged, 25 g) and wet dog food (375 g), pasteurized American cheese (25 g), peanut butter (25
26
g), dry dog food (25 g, 375 g), sprout irrigation water (375 g), raw head-on shrimp (25 g),
27
chicken carcass rinsate (30 mL), chicken carcass sponge, sealed/glazed ceramic tile, concrete,
28
stainless steel.)
29
30
Acknowledgements
31
32
We would like to extend a sincere thank you to the following collaborators for their dedicated
33
participation in this study:
34
35
Joanne Ruebl –Cherney Microbiological Services, Ltd, Green Bay, WI
36
Jessica Dyszel & Mathew Vross –Richter International, Columbus, OH
37
Vikas Gill – US FDA Center for Food Safety and Applied Nutrition, College Park, MD
38
Brad Stawick & Keith Blanchard - Microbac Laboratories, Inc., Warrendale, PA.
39
Mark Horan & Delando Lewis - Microbac Laboratories, Inc., Baltimore, MD
40
Indaue Mello – Mars Petcare, US, Kansas City, MO
41
Jodene Jurgens & Leslie Thompson – Aegis, North Sioux City, SD
42
David Bosco – Food Safety Net Services, Fresno, CA
43
Amit Morey & Sergio Montez – Food Safety Net Services, San Antonio, TX
44
Kyle Newman – Venture Laboratories, Inc., Lexington, KY
45
Mary Bandu & Matt Oltman, Chestnut Laboratory, Springfield, MO
46
Robert Brooks – ATC Microbiology, LLC., North Little Rock, AR
47