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10. After the assay is complete, remove the 3M Molecular Detection Speed Loader Tray from the 3M Molecular Detection
Instrument and dispose of the tubes by soaking in a 1-5% (v:v in water) household bleach solution for 1 hour and away
from the assay preparation area.
NOTICE: To minimize the risk of false positives due to cross-contamination, never open reagent tubes containing
amplied DNA. This includes 3M Reagent Control, 3M Molecular Detection Assay 2 - E. coli O157 (including H7)
Reagent Tube, and 3M Matrix Control Tubes. Always dispose of sealed reagent tubes by soaking in a 1-5% (v:v in
water) household bleach solution for 1 hour and away from the assay preparation area.
Results and Interpretation
An algorithm interprets the light output curve resulting from the detection of the nucleic acid amplication. Results are
analysed automatically by the software and are color-coded based on the result. A Positive or Negative result is determined
by analysis of a number of unique curve parameters. Presumptive positive results are reported in real-time while Negative
and Inspect results will be displayed after the run is completed.
Presumptive positive samples should be conrmed as per the laboratory standard operating procedures or by following
the appropriate reference method conrmation
(1,2,3)
, beginning with transfer from the primary BPW ISO enrichment to
secondary enrichment broth(s), followed by subsequent plating and conrmation of isolates using appropriate biochemical
and serological methods.
NOTE: Even a negative sample will not give a zero reading as the system and 3M Molecular Detection Assay 2 - E. coli
O157 (including H7) amplication reagents have a “background” relative light unit (RLU) reading.
In the rare event of any unusual light output, the algorithm labels this as “Inspect.” 3M recommends the user to repeat
the assay for any Inspect samples. If the result continues to be Inspect, proceed to conrmation test using your preferred
method or as specied by local regulations.
In the event of discordant results (presumptive positive with the 3M Molecular Detection Assay 2 - E. coli O157
(including H7), non-conrmed by one of the means described above, and in particular for the latex agglutination test),
the laboratory must follow the necessary steps to ensure the validity of the results obtained.
Conrmation of Results According to the NF VALIDATION Certied Method
In the context of the NF VALIDATION, all samples identied as positive by the 3M Molecular Detection Assay 2 - E. coli
O157 (including H7) must be conrmed by one of the following tests:
Option 1: Using the ISO 16654
(3)
standard starting from the buered peptone water
(3)
enrichment.
Option 2: Implementing a conrmation method consisting of the following: Streak 50 L of the buered peptone water
(3)
enrichment onto a Cexime Potassium Tellurite Sorbitol MacConkey (CT-SMAC)
(3)
agar plate. Incubate for 24 ±3 hours at
37°C. Streak characteristic colonies onto nutrient agar and perform latex agglutination test directly onto isolated colonies.
If the 3M Molecular Detection Assay 2 - E. coli O157 (including H7) results are not conrmed, perform an immunomagnetic
separation step and then streak 50 L onto CT-SMAC.
Option 3: Using nucleic acid probes as described in the EN ISO 7218
(5)
standard, performed on isolated colonies (puried
or not) from CT-SMAC (see Options 1 or 2). The nucleic acid probes must be dierent from those used in the 3M Molecular
Detection Assay 2 - E. coli O157 (including H7).
Option 4: Using any other method certied NF VALIDATION, the principle of which must be dierent from 3M Molecular
Detection Assay 2 - E. coli O157(including H7). The complete protocol described for this second validated method must be
used. All steps prior to the start of conrmation must be common to both methods.
In the event of discordant results (presumptive positive with the alternative method, non-conrmed by one of the means
described above) the laboratory must follow the necessary steps to ensure the validity of the result obtained.
If you have questions about specic applications or procedures, please visit our website at www.3M.com/foodsafety or
contact your local 3M representative or distributor.
Appendix A. Protocol Interruption: Storage and re-testing of samples
1. To store a heat-treated lysate, re-cap the lysis tube with a clean cap (see Lysis section, 4.5)
2. To store an enriched sample, incubate for a minimum of 18 hours prior to storage.
3. Store at 4 to 8°C for up to 72 hours.
4. Prepare a stored sample for amplication by inverting 2-3 times to mix.
5. Decap the tubes.
6. Place the mixed lysate tubes on 3M Molecular Detection Heat Block Insert and heat at 100 ± 1°C for 5 ± 1 minutes.
7. Remove the rack of 3M Lysis Solution tubes from the heating block and allow to cool in the 3M Molecular Detection
Chill Block Insert at least 5 minutes and a maximum of 10 minutes.
8. Continue the protocol at the Amplication section detailed above.