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Office of Regulatory Science
Center for Food Safety and Applied Nutrition
Food and Drug Administration
5100 Paint Branch Parkway, Rm 3E-021
College Park, MD 20740
Michael Brodsky
Brodsky Consultants
73 Donnamora Crescent
Thornhill, Ontario L3T 4K6
Canada
Yvonne Salfinger
Consultant
Denver, CO
Principle
3M Molecular Detection Assay
Salmonella
method is intended for use with the 3M Molecular Detection
System for the rapid and specific detection of
Salmonella
spp. in food, food-related, and environmental
samples after enrichment. The 3M Molecular Detection Assay
Salmonella
Test uses isothermal amplification
of unique DNA target sequences with high specificity, efficiency and rapidity, and bioluminescence to detect
the amplified sequences. Presumptive positive results are reported in real-time while negative results will be
displayed after the assay is completed.
The limit of detection of a method is defined as the lowest concentration point where reliable analytical results
can be obtained. This can vary with different serotypes. For the 3M Molecular Detection Assay
Salmonella
this
has been demonstrated to be 1-5 CFU/ 25 g of sample or 1-5 CFU/ swab.
As with all test methods, the source of enrichment medium can influence the results. The 3M Molecular
Detection Assay
Salmonella
has only been evaluated for use with the enrichment medium, 3M™ Buffered
Peptone Water (ISO) (BPW ISO). Matrices are incubated in 3M Buffered Peptone Water for 10-24 hours to
enrich for
Salmonella
prior to initiating the assay, with the exception of raw head-on shrimp, which requires an
additional, 4-24 hr secondary enrichment.
Study Summary
This report presents the analytical results of the method modification and matrix extension evaluation of the 3M
™
Molecular Detection Assay (MDA)
Salmonella.
The matrix extension included two separate studies 1) Internal
study: 10 additional matrices, two new enrichment protocols for specific matrices and 2) Independent study: two
additional matrices, two new enrichment protocols for specific matrices, conducted at AEGIS FOOD TESTING
Laboratories, Inc., North Sioux City, SD. All test kits and proprietary media unique to the 3M MDA
Salmonella
were provided by 3M Food Safety Department (St. Paul, Minnesota).
Materials and Methods
Testing was conducted following the procedures outlined in the AOAC Research Institute
Performance Test
Methods
SM
Program:
Modification/Matrix Extension Protocol for the 3M
TM
Molecular Detection Assay Salmonella.
The matrix extension portion of the validation included chicken carcass rinsate, chicken carcass sponges,
pasteurized American cheese, dry dog food (25 g, 375 g), creamy peanut butter, raw ground chicken (25 g, 325 g),
raw head-on shrimp, sprout irrigation water, concrete, sealed/glazed ceramic tile, and stainless steel. The method
modification included a higher enrichment temperature to 41.5±1
o
C and shorter enrichment time to 10 hours for raw
ground beef (25 g, 325 g, 375 g). Each matrix was analyzed after 18 hours of incubation with the exception of:
ground chicken, which was analyzed at 10, 12, 14, and 18 hours; raw ground beef, which was analyzed at 10, 12,
and 18 hours; and head-on shrimp, which was analyzed from a secondary enrichment, Rappaport Vasiliadis-10 broth
(RV-10), at 4 and 24 hours of incubation. The 3M MDA
Salmonella
assay was compared to the United States
Department of Agriculture/Food Safety Inspection Service Microbiological Laboratory Guidelines (USDA/FSIS
2013.09 /PTM Matrix Extension Report
March 2014
Expert Review Panel Use Only
AOAC Research Institute
Expert Review Panel Use O ly