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LPT method (foods)
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Pre-enrichment (25g)*: twenty 25g inoculated samples and five 25g uninoculated
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samples were added to 225 ml of LPT Broth (room temperature) in a filter stomacher
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bag. These were stomached for 2 minutes prior to incubation for 26-30 h at 30 ± 1°C.
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Following incubation, for all foods except chicken nuggets, 0.5ml of broth was
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transferred to sample well of the LPT test strip and heated for 5 ± 1 minutes on the
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VIDAS Heat& Go. The strip was then removed and left to cool at room temperature for
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10 minutes prior to performing the VIDAS test. For chicken nuggets 2-3 ml of
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enrichment was transferred to a tube and heated for 5 minutes in a boiling bath, then
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allowed cool before transferring 0.5ml to the VIDAS strip.
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*For the analysis of cantaloupe melons, an entire cantaloupe (600-900g) was combined
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with approximately 1 L of LPT Broth (room temperature) till the melon was completely
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submerged. Incubation conditions and analysis of samples was conducted according to
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procedures for 25g test portions.
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Pre-enrichment (125g): twenty 125g inoculated samples and five 125g uninoculated
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samples were added to 375 ml of LPT Broth (room temperature) in a filter stomacher
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bag. These were stomached for 2 minutes prior to incubation for 24-30 h at 30 ± 1°C.
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Following incubation, 1.0 ml was transferred from the primary enrichment to 10 ml LPT
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broth and incubated 22-26 h at 30 ± 1°C. From each secondary enrichment, 0.5ml of was
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transferred to sample well of the LPT test strip and heated for 5 ± 1 minutes on the
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VIDAS Heat& Go. The strip was then removed and left to cool at room temperature for
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10 minutes prior to performing the VIDAS test.
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Confirmation: For USDA method comparison, all enrichment broths were confirmed by
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transferring 0.1ml to 10ml Fraser both (FB) and incubating FB at 35±1°C for 48 h. Any
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FB showing blackening (24-48h) was streaked to Modified Oxford agar (MOX) agar. In
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addition, approximately 0.1ml LPT broth was also streaked directly to MOX agar then
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incubated for 24-48 h at 35 ± 1°C. At least one typical colony per sample/media was
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streaked to Horse blood overlay agar (HLA) and confirmed using standard biochemical
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tests. For the FDA-BAM and AOAC method comparisons, all enrichment broths were
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confirmed by streaking to Oxford and ALOA agar plates and continuing with
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biochemical confirmations.
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USDA/FSIS MLG 8.07
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Twenty 25g inoculated samples and five 25g uninoculated samples were added to 225 ml
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of University of Vermont Medium (UVM). These were stomached for 2 minutes then
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incubated at 30±1°C. After 20-24h, 0.1ml of the UVM enrichment was transferred to
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