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3M MDA2 E. coli O157:H7 Collaborative Study
May 2016
OMA-2016-May-XXXX
DRAFT DOCUMENT
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c)
Study Schedule
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a)
All data should be sent to the SD by the 2
nd
week of study.
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b)
The contract laboratory will prepare the test portions and ship the test portions refrigerated
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via overnight courier to the collaborators to arrive on a Friday. Test portion processing and
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analysis will begin on Monday. Data forms will be completed and faxed or emailed back to
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the co-Study Director by the following Friday.
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2)
Test Portion Preparation
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a)
Fresh raw ground beef will be obtained from local retail outlets and screened for the presence
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of
E. coli
O157. Naturally contaminated test portions will be used if available at sufficient levels.
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Alternatively, the test portions will be artificially inoculated to meet the targets of 0.2-2.0
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cfu/test portion for the low and 2 – 5 cfu/test portion for the high with the appropriate
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concentration of a wet inoculum.
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b)
Preparation of test portions
. A liquid inoculum will be added drop-wise to a bulk quantity of
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ground beef for each inoculation level - 0.2-2 cfu/25g and 2-5 cfu/25g. The bulk quantity will
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then be mixed to achieve equal distribution of analyte throughout. Test portions (25g) will be
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pulled from this bulk lot and randomly assigned to the reference method or the 3M MDA2 -
E.
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coli
O157 (including H7) method. An additional 300g uncontaminated raw ground beef will be
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added to the 25g test portion resulting in a 325g test portion. The test portions will be stored at
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2-8
C for 72-96 h prior to testing.
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c)
Shipment of test portions.
Test portions will be packaged in leak-proof, insulated containers
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and shipped (according to the Dangerous Goods Regulations IATA for Infections Substances) by
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overnight carrier to arrive the day before initiation of analysis
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All refrigerated test portions will
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be packed with ice packs to maintain a temperature of <7
C during transport. A temperature
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control sample will be included with each shipment to verify temperature of sample upon
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receipt. Upon arrival, the ground beef test portions will be stored at 2-8
C until they are
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analyzed.
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d)
Microbiological analysis.
The test portion preparation is different for the 3M MDA2 -
E. coli
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O157 and reference methods. Therefore, each collaborator will receive a separate test portion
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for each method. They will be instructed to test 325 g ground beef using the 3M MDA2 -
E. coli
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O157 method and another 325 g ground beef using the MLG reference method. The Reference
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Method Confirmation procedures will be performed starting with the secondary enrichment
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steps. The recovered isolates will be identified by the API20E (Official Method 978.24) or the
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VITEK2 GN (Official Method 2011.17). The somatic (O) and flagellar (H) tests will also be
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performed.
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One additional control (negative) test portion will be provided to each collaborator for each
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matrix to determine the total plate count on the day of analysis.
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OMAMAN-35 B: Collaborative Study Protocol
ERP USE ONLY
January 2017
AOAC Research Institut
Expert Review Panel Use Only