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3M Petrifilm SALX Collaborative Study July 2013
OMA-2013-July-XXX
DRAFT DOCUMENT 16
Food Type Reference Reference
Pre-enrichment
3M Petrifilm SALX
1° Enrichment
3M Petrifilm SALX
2° Enrichment
Raw ground
beef (80/20)
25g-SALX
25g-MLG
USDA-MLG BPW
3M Salmonella
enrichment +
supplement
Rappaport-Vassiliadis
R10 (R-V R10) Broth
Dry dog food
375g-SALX
25g-BAM
FDA-BAM Lactose broth
3M Salmonella
enrichment +
supplement
None
1
2
1.0 Ground beef - 3M Petrifilm SALX 3
1.1 Aseptically add the 25g test portion to 225 mL pre-warmed (41.5°C) 3M Salmonella 4
Enrichment Base with supplement. 5
1.2 Mix in a Stomacher® bag with filter for 2 min. 6
1.3 Incubate 18-24 hr at 41.5 ± 1°C. 7
1.4 After primary enrichment incubation, transfer 0.1 mL of the primary enrichment into 10 8
mL Rappaport-Vassiliadis R10 (R-V R10) Broth. Incubate at 41.5 ± 1.0°C for 8-24 hours. 9
1.5 Prior to analysis, hydrate the 3M Petrifilm SALX Plates using 2.0 mL of sterile distilled 10
water. After hydration, the liquid was spread across of the surface of the plate using a 11
plastic spreader to evenly distribute the diluent. The plates were left undisturbed and 12
protected from light for a minimum of 1 hour prior to use. 13
1.6 Streak each enriched test portion onto 3M Petrifilm SALX plate and incubate at 41.5° ± 14
1°C for 24 ± 2 hours. 15
16
1.7 Alternative 3M SALX Confirmation Method 17
1.7.1 Using a fine tip marker, circle presumptive positive colonies (red to brown 18
colonies with discrete yellow zones and/or gas bubbles) on the plate top film. 19
1.7.2 Lift the top film and place a 3M Petrifilm Salmonella Express Confirmation Disk 20
onto the gel. Close the film using a gloved hand (while practicing good 21
laboratory technique) and remove air bubbles by gently applying a sweeping 22
motion with even pressure onto the top of the film with the analyst’s fingers. 23
1.7.3 Incubate the plates with confirmation disks at 41.5° ± 1°C for 4 to 5 hours. 24
1.7.4 Observe circled colonies for color change - red/brown to green blue, blue, dark 25
blue or black confirm the colony as Salmonella species. No color change, colony 26
is negative. 27
1.7.5 Transfer typical colonies from SALX plate to TSI/LIA slants. Incubate 35 ± 1°C for 28
24 ± 2h. 29
1.7.6 Confirm a minimum of one typical colony per test portion with 30
biochemical/serological procedures prescribed by the USDA/FSIS method. Either 31
the API20E (Official Method 978.24) or the VITEK GN (Official Method 2011.17) 32
will be used as an alternative to the conventional biochemical tests. The 33
somatic (O) and flagellar (H) tests will also be performed. 34
2
3
OMAMAN-08/Collaborative Study Protocol
March 2014
Expert Review Panel Use Only
AOAC Research Institute
Expert Review Panel Use Only