AOAC-RI ERP Book Micro Jan 19 2017

Sample Preparation (a) Performing Pre-Enrichment: 3M MDA 2 - E. coli O157 1) Raw Ground Beef

A 325 g test portion is aseptically combined with 975 ± 19.5 mL (1 L) of pre-warmed (41.5 ± 1°C) ISO-BPW in a filtered enrichment bags.

2) Homogenize for 2 ± 0.2 minutes. 3) Incubate at 41.5 ± 1°C for 10 hours. 4) Following incubation, a sample aliquot will be removed to be prepared by 3M MDA 2 - E. coli O157 method. Lysis Workflow Procedures (a) Lysis 3M MDA 2 - E. coli O157 process 1) Allow the lysis solution (LS) tubes to warm to room temperature (20- 25° C) over night (16 – 18 hours). Alternatives to equilibrate the LS tubes at room temperature are to set the LS tubes on the laboratory bench for at least 2 hours, incubate the LS tubes in a 37 ± 1°C incubator for 1 hour or place them in a dry double block heater for 30 seconds at 100° C. 2) Invert the capped tubes to mix. Proceed to the next step within 4 hours. 3) Remove the enrichment broth from the incubator. 4) Use the 3M ™ Molecular Detection Cap/Decap Tool-Lysis to decap one LS tube strip- one strip at a time. 5) Discard the LS cap. 6) Transfer 20 µL of sample into a LS tube. 7) Repeat step 6 until each individual sample has been added to a corresponding LS tube in the strip. 8) When all samples have been transferred, transfer 20 µL of Negative Control (sterile enrichment medium) into a LS tube. 9) Verify that the temperature of the 3M Molecular Detection Heat Block Insert is at 100 ± 1° C

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