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Revised Mar 2014
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For over 100 years,
Salmonella
, one of the most frequently reported causes of foodborne
2
outbreaks, has been known to cause foodborne illness in humans [1]. The bacterium has been
3
implicated in outbreaks from a variety of foods including raw animal products, such as meat,
4
poultry, eggs, dairy products, seafood as well as some fruits and vegetables [2]. In order to
5
reduce outbreaks of Salmonellosis, a comprehensive farm-to-fork approach is needed. The
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detection of
Salmonella
can often be very time consuming and expensive, as the presence of the
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microorganism in food usually does not affect the taste, smell or appearance [3]. The 3M
™
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Molecular Detection Assay (MDA)
Salmonella
method, in conjunction with 3M
™
Buffered
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Peptone Water ISO (BPW ISO)[4], uses isothermal amplification of nucleic acid sequences to
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detect
Salmonella
in enriched food, feed and environmental samples.
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The 3M MDA
Salmonella
method allows for next-day detection of
Salmonella
species.
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After 10-24 hours of enrichment using pre-warmed (37 ± 1
o
Cor 41.5
o
C) 3M BPW ISO medium,
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Salmonella
detection is performed by the 3M MDA
Salmonella.
For one matrix (raw head-on
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shrimp) a short secondary enrichment in Rappaport Vasiliadis 10 broth (RV10, 4-24Hrs) is
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required.Presumptive positive results are reported in real-time while negative results are
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displayed after completion of the assay.
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Prior to the collaborative study, the 3M MDA
Salmonella
method was certified as a
Performance
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Tested Method
(PTM) following the AOAC Guidelines for Harmonized PTM Studies [5]. The
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aim of the PTM study was to demonstrate that the 3M MDA
Salmonella
method could detect
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Salmonella
in selected foods as claimed by the manufacturer. For the 3M MDA
Salmonella
21
evaluation, there were 6 matrices analyzed: raw ground beef (25 g), cookedbreaded chicken
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(325 g), pasteurizedliquid wholeegg (100 g), rawshrimp (head-off,25 g), fresh spinach
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(bagged,25 g) and wet dog food (375 g)with the primary enrichment incubated at 37 ± 1
o
C for
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18-24 hours.
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A matrix extension/method modification was performed post-collaborative study with the
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following: 1) A matrix extension to the existing claim, including pasteurized American cheese
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(25 g), dry dog food (25 g, 375 g), creamy peanut butter (25 g), sprout irrigation water (375 mL)
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enriched at 37 ± 1
o
C; 2) A matrix extension to the existing claim, including chicken carcass
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rinsate (30 mL), chicken carcass sponges, raw ground chicken (25 g, 10-18 hr) and raw ground
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chicken (325 g, 14-18 hr), concrete, sealed/glazedceramic tile, and stainless steel enriched at 41.5
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± 1
o
C, and raw head-on shrimp enriched at 37 ± 1
o
C 18-24 hrs with a secondary enrichment at
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41.5 ± 1
o
C for 4-14 hrs.; 3) A method modification involving a shorter enrichment time and
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higher enrichment temperature to 41.5
±1
o
C for raw ground beef (25 g, 325 g, 375 g; 10-18 hr),
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All other PTM parameters (inclusivity, exclusivity, ruggedness, stability and lot to lot
35
variability) tested in the PTM studies satisfied the performance requirements for PTM approval.
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The method was awarded PTM certification number 031208 on March 30, 2012. The matrix
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extension/modification study was approved on January 31, 2014.
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The aim of this collaborative study was to compare the 3M MDA
Salmonella
method to the
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United States Department of Agriculture (USDA)Food Safety Inspection Service (FSIS) -
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Microbiology Laboratory Guidebook (MLG) 4.05 [6]for raw ground beef and the US Food and
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Drug Administration (FDA) Bacterial Analytical Manual (BAM)Chapter 5 [7] method for wet
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dog food.
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Collaborative Study
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Study Design
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