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reducing the potential for contamination with one or more molecules of amplified PCR product in
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future tests.
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Fluorescent real time detection
[1] - This automated BAX® System method uses fluorescent
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detection to analyze PCR product. One PCR primer for each target (one
Salmonella-
specific target
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and an internal control) contains a fluorescent dye (two different dyes, one for each target) as a
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constituent of the primer as well as a quencher (the uni-molecular combination of a primer,
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fluorescent dye and quencher constitute a Scorpion™ probe). When not incorporated into a PCR
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product, the Scorpion™ probe has a hair-pin loop structure which keeps the dye and quencher in
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close proximity. When incorporated into a PCR product, the dye and quencher are spatially
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separated due to an internal hybridization, which causes an increase in emission signal.
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The BAX® System measures the magnitude and characteristics of fluorescent signal change
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during each cycle of PCR. The data points generated are analyzed using an algorithm which
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evaluates the increase in signal intensity, the slope of the rise relative to increase in signal, and the
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noisiness of the baseline for each sample. If the amplification plot represents the sigmoid shape
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characteristic of the targeted PCR response, the software assigns a positive result to that sample. If
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there is no evidence of the exponential amplification event, the software assigns a negative result to
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that sample. In cases where there is anomalous data, such as an unexpected degree of noise or a
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large rise in fluorescence which cannot be modeled as an exponential amplification, the software
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assigns an indeterminate result.
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6. GENERAL INFORMATION
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Salmonella
is a foodborne pathogen that traditionally has been screened for by culture
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methods, such as those of the Bacteriological Analytical Manual (BAM) of the United States
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Food and Drug Administration [2], the Health Canada Compendium of Analytical Methods [3],
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and the Microbiological Laboratory Guidebook (MLG) of the United States Department of
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Agriculture Food Safety and Inspection Service (USDA-FSIS)
[4]. These culture methods each
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require at least three days for a negative result and often many more days if there are potential
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Dupont BAX Salmonella PTM Report
Modification Approved 2012 / PTM Certification No. 081201
For Expert Review Panel Use Only
Do Not Distribute