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3M Petrifilm SALX Collaborative Study
July 2013
OMA-2013-July-XXX
DRAFT DOCUMENT
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1.0
INTRODUCTION
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The goal of this collaborative study is to estimate the following performance parameters of
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the 3M™ Petrifilm™ Salmonella Express (SALX) System: probability of detection (POD) and the
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difference in the POD at 3 contamination levels for both the candidate and reference
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methods. Test portions from 3 different contamination levels, including negative controls, will
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be sent to collaborators where they will perform the 3M Petrifilm SALX method along with the
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corresponding reference method. Raw fresh ground beef will be tested at 25g and dry dog
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food will be tested at 375g.
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1.1
Description of the 3M Petrifilm SALX Method
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The 3M Petrifilm SALX method is intended for the rapid and specific detection and
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biochemical confirmation of
Salmonella
from food and food process environmental
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samples after enrichment in 3M™
Salmonella
Enrichment Base with the added 3M™
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Salmonella
Enrichment Supplement. The 3M™ Petrifilm™ Salmonella Express Plate is a
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s
ia
mple ready-to-use chromogenic culture medium system that contains a cold-water-
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soluble gelling agent and is selective and differential for
Salmonella,
providing a
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presumptive result in as little as 44 hours from low microbial background foods (≤10
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cfu/g), and 52 hours from high microbial background foods (≥10
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cfu/g). The 3M™
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Petrifilm™ Salmonella Express Confirmation Disk contains a biochemical substrate that
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facilitates the biochemical confirmation of
Salmonella
organisms
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1.2
Summary of PTM/Precollaborative Study
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The 3M Petrifilm SALX method was validated according to AOAC Guidelines (2002) in a
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harmonized PTM/OMA study. The aim of this study was to demonstrate that the 3M
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Petrifilm SALX method could detect
Salmonella
in select foods as claimed by the
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manufacturer.
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The 3M Petrifilm Salmonella Express System was evaluated following the AOAC
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Performance Tested Methods
requirements: inclusivity/exclusivity, ruggedness,
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stability/lot to lot consistency and method comparison. The 3M Petrifilm SALX method
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was compared to the USDA/FSIS-MLG 4.05
Isolation and Identification of Salmonella
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from Meat, Poultry, Pasteurized Egg and Catfish Products
for raw ground chicken,
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pasteurized liquid whole egg, raw ground beef, raw ground pork, and cooked chicken
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nuggets and to FDA/BAM Chapter 5
Salmonella
for frozen uncooked shrimp, fresh
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bunched spinach, dry dog food, and stainless steel.
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Overall the assay was equivalent to the reference methods based on the Chi square
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test for significant difference and the Probability of Detection (POD). There were
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no unexpected results in all of the other PTM requirements.
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The 3M Petrifilm Salmonella Express System is sufficiently rugged to withstand
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small variations in the experimental parameters of enrichment incubation time and
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temperature, plate incubation time and temperature, disk incubation time and
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temperature and various plate hydration options. Each parameter was tested
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using both the high and low microbial load methods as described in the Instructions
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OMAMAN-08/Collaborative Study Protocol
March 2014
Expert Review Panel Use Only
AOAC Research Institute
Expert Review Panel Use Only