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3M Petrifilm SALX Collaborative Study
July 2013
OMA-2013-July-XXX
DRAFT DOCUMENT
17
1
1.8
Reference Method Confirmation
2
1.8.1
Transfer 0.5
±
0.05 mL 3M SALX enriched sample into 10 mL tetrathionate (TT-
3
Hajna) broth and 0.1
±
0.02 mL into 10 mL modified Rappaport-Vassiliadis (mRV)
4
broth. Incubate at 42
±
0.5
°
C for 22-24 h.
5
1.8.2
Streak both secondary enrichments onto double modified lysine iron agar
6
(DMLIA) or xylose lysine Tergitol (XLT4) agar and brilliant green sulfa (BGS) agar.
7
Use one loopful of inoculum for each plate. Incubate 35
±
2
°
C for 18-24h. Select
8
colonies. Re-incubate all plates for an additional 18-24 h. Reexamine initially
9
negative plates and pick colonies as above.
10
1.8.3
Transfer typical colonies to TSI/LIA slants. Incubate 35
±
1
°
C for 24
±
2h.
11
1.8.4
Confirm a minimum of one typical colony per sample with
12
biochemical/serological procedures prescribed by the USDA/FSIS method. Either
13
the API20E (Official Method 978.24) or the VITEK GN (Official Method 2011.17)
14
will be used as an alternative to the conventional biochemical tests. The
15
somatic (O) and flagellar (H) tests will also be performed.
16
17
2.0
USDA-FSIS MLG Ch. 4.06 – Ground beef
18
2.1
To each 25g test portion, add 225 mL buffered peptone water. Stomach each sample for
19
approximately two minutes. Incubate at 35
±
1
°
C for 22
±
2h.
20
2.2
Transfer 0.5
±
0.05 mL enriched sample into 10 mL tetrathionate (TT-Hajna) broth and
21
0.1
±
0.02 mL into 10 mL modified Rappaport-Vassiliadis (mRV) broth. Incubate at 42
±
22
0.5
°
C for 22-24 h.
23
2.3
Streak both secondary enrichments onto double modified lysine iron agar (DMLIA) or
24
xylose lysine Tergitol (XLT4) agar and brilliant green sulfa (BGS) agar. Use one loopful of
25
inoculum for each plate. Incubate 35
±
2
°
C for 18-24h. Select colonies. Re-incubate all
26
plates for an additional 18-24 h. Reexamine initially negative plates and pick colonies as
27
above.
28
2.4
Transfer typical colonies to TSI/LIA slants. Incubate 35
±
1
°
C for 24
±
2h.
29
2.5
Confirm a minimum of one typical colony per sample with biochemical/serological
30
procedures prescribed by the USDA/FSIS method. Either the API20E (Official Method
31
978.24) or the VITEK GN (Official Method 2011.17) will be used as an alternative to the
32
conventional biochemical tests. The somatic (O) and flagellar (H) tests will also be
33
performed.
34
35
3.0
Dry dog food - 3M Petrifilm SALX:
Aseptically add the 375g test portion to 3375 mL pre-warmed
36
(41.5°C) 3M
Salmonella
Enrichment Base with supplement.
37
3.1
Mix in a Stomacher® bag with filter for 2 min.
38
3.2
Incubate 18-24 hr at 41.5 ± 1°C.
39
3.3
Prior to analysis, hydrate the 3M Petrifilm SALX Plates using 2.0 mL of sterile distilled
40
water. After hydration, the liquid was spread across of the surface of the plate using a
41
plastic spreader to evenly distribute the diluent. The plates were left undisturbed and
42
protected from light for a minimum of 1 hour prior to use.
43
3.4
Streak each enriched test portion onto 3M Petrifilm SALX plate and incubate at 41.5° ±
44
1°C for 24 ± 2 hours.
45
3.5
After incubation, record presumptive positive or negative result.
46
3.5.1
Positive – red to brown with yellow zone or gas bubble
47
OMAMAN-08/Collaborative Study Protocol
March 2014
Expert Review Panel Use Only
AOAC Research Institute
Expert Review Panel Use Only