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7. PRINCIPLE
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PCR amplification
- The BAX® System uses the Polymerase Chain Reaction (PCR) to amplify a
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specific fragment of bacterial DNA, which is stable and unaffected by growth environment. The
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fragment is a genetic sequence that is unique to the genus
Salmonella
, thus providing a highly
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reliable indicator that the organism is present. The BAX® System simplifies the PCR process by
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combining the requisite primers, polymerase and nucleotides into a stable, dry, manufactured tablet
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already packaged inside the PCR tubes. After amplification, these tubes remain sealed thus
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significantly reducing the potential for contamination with one or more molecules of amplified PCR
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product in 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. The BAX®
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System measures the magnitude and characteristics of fluorescent signal change. An analysis by
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the BAX® System software algorithm then evaluates that data to determine a positive or negative
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result which is displayed as described below.
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8. 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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Dupont BAX Salmonella PTM Report
PTM Certification No. 081201 (08/07/2012)
For Expert Review Panel Use Only
Do Not Distribute