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3M Petrifilm SALX Collaborative Study
July 2013
OMA-2013-July-XXX
DRAFT DOCUMENT
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a.
On the 3M Petrifilm SALX Plate top film,
circle up to five isolated presumptive positive
1
Salmonella
colonies using a permanent, ultra fine tip marker
(figure I).
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b.
Biochemically confirm all
Salmonella
presumptive positive results using the 3M Petrifilm
3
SALX Confirmation Disk. See the Biochemical Confirmation section.
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5
Note:
If the 3M Petrifilm SALX Plates cannot be analyzed within 1 hour of removal from the
6
incubator
, first circle the presumptive
Salmonella
colonies on the top film by using a
7
permanent, ultra fine tip marker
and then place the plates in a sealed plastic bag for later
8
analysis. Protect 3M Petrifilm SALX Plates from light and store at -20 to -10°C for no longer than
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72 hours. Allow plates to warm to room temperature (20-25°C / <60% RH) before adding the
10
disk to the plate.
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WARNING:
To reduce the risks associated with a false-negative result leading to the release of
13
contaminated product and the possibility of false positive results requiring a retest, always use a
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permanent, ultra fine tip marker to circle the characteristic presumptive
Salmonella
colonies on the
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top film of the 3M Petrifilm SALX Plate before appropriate storage of the plate and/or before placing
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the 3M Petrifilm SALX Confirmation Disk onto the gel.
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5.11
BIOCHEMICAL CONFIRMATION – 3M Petrifilm SALX Confirmation Disk
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5.11.1
NOTE:
Use good laboratory practices to avoid cross contamination and/or
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direct contact with the 3M Petrifilm SALX Plate and/or 3M Petrifilm SALX
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Confirmation Disk.
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5.11.2
Remove an individually packaged 3M Petrifilm SALX Confirmation Disk from its
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pouch and allow it to come to room temperature (20-25°C / <60% RH). Then
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remove the 3M Petrifilm SALX Confirmation Disk from its individual package by
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peeling the package to expose the 3M Petrifilm SALX Confirmation Disk’s tab,
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grasping the tab with a gloved hand, and removing the 3M Petrifilm SALX
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Confirmation Disk.
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5.11.3
Lift the top film (with the already circled presumptive
Salmonella
colonies) of
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the 3M Petrifilm SALX Plate and insert the 3M Petrifilm SALX Confirmation Disk
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by rolling it onto the gel to avoid entrapping air bubbles (figure J). Close the 3M
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Petrifilm SALX Plate.
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5.11.4
Using a gloved hand, gently apply a sweeping motion with even pressure onto
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the top film to remove any air bubbles in the inoculation area and assure good
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contact between the gel and the 3M Petrifilm SALX Confirmation Disk (figure K).
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5.11.5
Incubate the 3M Petrifilm SALX System (plate and disk) at 41.5 ± 1.0
°
C for 4 - 5
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hours in a horizontal position, colored side up, no higher than 20 plates.
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5.11.6
Remove the 3M Petrifilm SALX System from the incubator and proceed with
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reading the results.
Only interpret the results for the circled presumptive
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Salmonella
colonies:
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5.11.6.1
Biochemically confirmed positive results: Colonies that are
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green to blue, blue to dark blue, or black or have a blue precipitate
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around them are biochemically confirmed positive for
Salmonella
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species.
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5.11.6.2
Biochemically confirmed negative results: Colonies that remain
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the same red, dark red or brown color without a blue precipitate are
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negative for
Salmonella
species.
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OMAMAN-08/Collaborative Study Protocol
March 2014
Expert Review Panel Use Only
AOAC Research Institute
Expert Review Panel Use Only