75 / 453
11
In the rare event of any unusual light output, the algorithm labels this as “Inspect.” 3M recommends the user to
1
repeat the assay for any Inspect samples. If the result continues to be Inspect, proceed to confirmation test using
2
your preferred method or as specified by local regulations.
3
4
In the event of discordant results (presumptive positive with the 3M Molecular Detection Assay 2 -
E. coli
O157
5
(including H7), non-confirmed by one of the means described above, and in particular for the latex agglutination
6
test), the laboratory must follow the necessary steps to ensure the validity of the results obtained.
7
8
If you have questions about specific applications or procedures, please visit our website at
9
www.3M.com/foodsafetyor contact your local 3M representative or distributor.
0
1
Appendix A. Protocol Interruption: Storage and re-testing of heat-treated lysates
2
1.
To store a heat-treated lysate, re-cap the lysis tube with a clean cap (see “LYSIS”, 4.5)
3
2.
Store at 4 to 8°C for up to 72 hours.
4
3.
Prepare a stored sample for amplification by inverting 2-3 times to mix.
5
4.
Decap the tubes.
6
5.
Place the mixed lysate tubes on 3M Molecular Detection Heat Block Insert and heat at 100 ±1°C for 5 ±1
7
minutes.
8
6.
Remove the rack of LS tubes from the heating block and allow to cool in the 3M Molecular Detection Chill
9
Block Insert at least 5 minutes and a maximum of 10 minutes.
0
7.
Continue the protocol at the ‘Amplification’ section detailed above.
1
2
Results of Collaborative Study
3
4
For this qualitative, unpaired collaborative study, the 3M Molecular Detection Assay (MDA) 2 –
E. coli
O157
5
(including H7) method was compared to the USDA FSIS MLG 5.09 reference method for raw ground beef (325
6
g). A total of 15 laboratories throughout the United Statesparticipated in this study, with 10 laboratories
7
submitting data for the raw ground beef. See Table 1 for a summary of laboratory participation. Each laboratory
8
analyzed 36 test portions for each method: 12 inoculated with a high level of
E. coli
O157:H7, 12 inoculated with a
9
low level of
E. coli
O157:H7, and 12 un-inoculated controls.
0
A background screen of the matrix indicated an absence of indigenous
E. coli
O157:H7 in the ground beef.Due to
1
the amount of raw ground beef needed for the evaluation (~900lbs.), ten (10) replicate 325 g test portionswere
2
screened for
E. coli
O157:H7. All test portions produced negative results for the target analyte.
3
The individual laboratory and sample results are presented in Table1 of the Supplementary Materials.
4
Table2016.1A summarizes the inter-laboratory results forthe ground beef, including POD statistical analysis [9].
5
As per criteria outlined in Appendix J of the AOAC Validation Guidelines, fractional positive results were
6
obtained.For each matrix, the level of
E. coli
O157:H7was determined by MPN on the day of initiation of analysis
7
by the coordinating laboratory. MPN results are presented in Tables 2016.2A.The APCresults for each
8
collaborating laboratory are presented in Table 2of the Supplementary Materials.
9
0
Raw Ground Beef (73% Lean) (325 g Test Portions)
1
2
Raw ground beef test portions were inoculated at a low and high level and were analyzed (Table 1 of the
3
Supplementary Materials) for the detection of
E. coli
O157:H7. Un-inoculated controls were included in each
4
analysis. Laboratory 3 was unable to confirm their samples using the USDA method, Laboratory 7
5
reportedcontamination of the E buffer and was not able to return to the enrichments to re-confirm, Laboratory 10,
6
13, and 15 did not follow the alternative method such that results could not be used. All other laboratories
7
submitted a full set of data for each method. The MPN levels obtained for this test portion, with 95% confidence
8
OMAMAN-35 A : Collaborative Study Manuscript
For ERP Use Only
January 2017
AOAC Research Institute
Expert Review P nel Use Only