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A Matrix Extension and Method Modification of the 3M
™
Molecular Detection Assay
Salmonella
for the
Detection of
Salmonella
species in a Variety of Foods and Environmental Surfaces
AOAC Research Institute
Modification/ Matrix Extension Evaluation
Abstract
A method modification and matrix extension evaluation of the 3M
™
Molecular Detection Assay (MDA)
Salmonella
was conducted to evaluate the 3M MDA
Salmonella’s
ability to detect
Salmonella
species in a variety of foods and
environmental surfaces. The 3M MDA
Salmonella
method was compared to the United States Department of
Agriculture/Food Safety Inspection Service Microbiological Laboratory Guidelines 4.06 Isolation and Identification
of
Salmonella
from Red Meat, Poultry, Egg and Environmental Samples and the Food and Drug Administration-
Bacterialogical Analytical Manual Chapter 5: Detection and Enumeration of
Salmonella
reference methods. The
3M MDA
Salmonella
and reference methods were analyzed by testing each matrix at three contamination levels: 20
replicates at a low-level of 0.2-2.0 CFU/test portion, 5 replicates at a high-level of 2-5 CFU/test portion, and 5
replicates at an un-inoculated control level of 0 CFU/test portion. The matrix extension included 10 food matrices
and 3 environmental surfaces: 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 for raw ground beef (25 g, 325 g,
375 g). The 3M MDA
Salmonella
detected
Salmonella
species after 18 hours incubation or less in all matrices
excluding shrimp. For raw head-on shrimp, the 3M MDA Salmonella method included a 4-24 hour secondary
enrichment and was able to reliably detect
Salmonella
after 22 hours incubation. Based on final incubation times
determined for each matrix, there were no statistically significant differences between 3M MDA
Salmonella
and the
reference methods for all matrices analyzed in this study. An inclusivity and exclusivity evaluation was conducted
using both method modification procedures. All inclusivity isolates were correctly detected, and all exclusivity
isolates were correctly excluded. The 3M MDA
Salmonella
demonstrated reliability as a rapid and sensitive method
for the detection of
Salmonella
species in a variety of foods and environmental surfaces: 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 ground beef (25 g, 325 g, 375 g), raw head-on shrimp, sprout irrigation water,
concrete, sealed/glazed ceramic tile, and stainless steel
Method Author
DeAnn L. Benesh
3M Food Safety Department
3M Center - Bldg 260-6B-01
St. Paul, MN 55144-1000
Submitting Company
3M Company
Food Safety Department
3M Center, Bldg. 275-5W-05
St. Paul, MN 55144-1000
Contract Laboratory
Q Laboratories, Inc.
Cincinnati, OH
Independent Laboratory
Aegis Food Testing Laboratories, Inc.
North Sioux City, SD
Reviewers
Thomas Hammack
Microbial Methods Development Branch
Division of Microbiology
2013.09 /PTM Matrix Extension Report
March 2014
Expert Review Panel Use Only
AOAC Research Institute
Expert Review Panel Use Only