314 / 1195
Revised Mar 2014
4
conducted according to either the USDA/FSIS-MLG 4.05 or FDA/BAM Chapter 5 reference
1
method, dependent on the matrix.
2
3
Test Portion Distribution
4
5
All samples were labeled with a randomized, blind-coded 3 digit number affixed to the
6
sample container. Test portions were shipped on a Thursday via overnight delivery according to
7
the Category B Dangerous Goods shipment regulations set forth by International Air Transport
8
Association (IATA). All samples were packed with cold packs to target a temperature of < 7°C
9
during shipment. Upon receipt, samples were held by the collaborating laboratory at refrigerated
10
temperature (3-5°C) until the following Monday when analysis was initiated. In addition to each
11
of the test portions and the total plate count replicate, collaborators also received a test portion
12
for each matrix labeled as “temperature control”. Participants were instructed to record the
13
temperature of this portion upon receipt of the shipment, document results on the Sample Receipt
14
Confirmation form provided and fax to the study director.
15
Additional shipments of raw ground beef test portions were made by the sponsoring laboratory
16
when aberrant results were observed. Further investigation of the results indicated that each
17
participating collaborator detected the presence of the target analyte in the un-inoculated control
18
samples sent in the first shipment. In each case, the same species was reported for the control
19
samples, which may have been due to cross-contamination. As a result, new test portions of raw
20
ground beef were shipped and analyzed by each of the collaborating laboratories as previously
21
described.
22
23
Test Portion Analysis
24
25
Collaborators followed the appropriate preparation and analysis protocol according to the
26
method for each matrix. For both matrices, each collaborator received 72 test portions of each
27
food product (12 high, 12 low and 12 controls for each method). For the analysis of the raw
28
ground beef test portions by the 3M MDA
Salmonella
method, a 25 g portion was enriched with
29
225 mL of pre-warmed (37 ±1
o
C) 3M BPW ISO, homogenized for 2 minutes and incubated for
30
18-24 hours at 37 ±1
o
C. For the wet dog food test portions analyzed by the 3M MDA
31
Salmonella
method, a 375 g portion was enriched with 3375 mL pre-warmed (37 ±1
o
C) 3M
32
BPW ISO, homogenized for 2 minutes and incubated for 18-24 hours at 37 ±1
o
C.
33
Following enrichment, samples were assayed by the 3M MDA
Salmonella
method and
34
confirmed following the standard reference method. Both test portion sizes analyzed by the 3M
35
MDA
Salmonella
method were compared to samples (25 g) analyzed using either the
36
USDA/FSIS-MLG or FDA/BAM reference method in an unpaired study design. All positive test
37
portions were biochemically confirmed by the API 20E biochemical test, AOAC Official
38
Method 978.24 or by the VITEK 2 GN identification test, AOAC Official Method 2011.17.
39
Serological testing was also performed.
40
41
Statistical Analysis
42
43
Each collaborating laboratory recorded results for the reference method and the 3M MDA
44
Salmonella
method on the data sheets provided. The data sheets were submitted to the study
45
director at the end of each week of testing for analysis. The results of each test portion for each
46
sample were compiled by the study director and the qualitative 3M MDA
Salmonella
results
47