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AOAC INTERNATIONAL
19. INCLUSIVITY / EXCLUSIVITY STUDY
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Methodology
– An evaluation was performed to test the inclusivity of the test method using the
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media specified for the assay. Exclusivity of the test method was performed using non-selective
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(BHI) broth.
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The inclusivity panel originated from a wide range of food, environmental, human and veterinary
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clinical diagnostic and animal non-diagnostic samples. Inclusivity strains (n=317 representing
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more than 100 serotypes) were included. The exclusivity panel of
non-
Salmonella
strains (n= 46
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representing 37 bacterial species) were chosen from the DuPont Qualicon Culture Collection.
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Most of these isolates were originally obtained from naturally contaminated food and food
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processing environmental samples or from animal sources, and all identifications were confirmed
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bio-chemically and/or serologically as appropriate.
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Cultures were struck for purity on BHI agar. For each strain, one colony was inoculated into a
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tube containing BHI broth (exclusivity testing) or test broth enrichment (inclusivity testing).
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Cultures were incubated overnight at 35ºC (exclusivity) or 41ºC (inclusivity) to reach cell densities
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of approximately 10
9
bacterial cells per mL. For exclusivity testing, cultures were tested with no
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dilution. For inclusivity testing, cultures were diluted to ~10
5
cfu/mL, which is 1 log over the
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claimed sensitivity of the assay.
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Results
- All isolates of
Salmonella
gave positive results at the cell density tested with the
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exception of one strain, DD1560, a
Salmonella enterica
Westpark, which is a subspecies II strain,
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originating from a tortoise intestine. Multiple replicates tested showed a consistent limit of
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detection of 10
6
cfu/ml for this strain, likely due to a DNA change in one of the priming sites or the
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Scorpion™ probe binding site. All non-
Salmonella
tested gave a negative result.
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Dupont BAX Salmonella PTM Report
PTM Certification No. 081201 (08/07/2012)
For Expert Review Panel Use Only
Do Not Distribute