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AOAC INTERNATIONAL
MODIFICATION TO THE BAX® SYSTEM REAL-TIME PCR ASSAY FOR
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SALMONELLA
(
PERFORMANCE TESTED METHOD
SM
#081201) IN
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SELECTED FOODS: ADDITION OF EIGHT PCR CYCLES TO IMPROVE
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SENSITIVITY
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1. ABSTRACT
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In August 2012, the AOAC Research Institute (AOAC-RI) certified the BAX® System Real-Time
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PCR Assay for
Salmonella
as comparable to the USDA-FSIS, U.S. FDA and Health Canada reference
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methods for detecting
Salmonella
in raw ground beef, chicken carcass rinses, cream cheese, bagged
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lettuce, dry pet food and stainless steel environmental samples.
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Since then, expanded use in real-world samples and additional research suggests that results for
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low-level positive samples could be improved by slightly extending the processing time. Internal studies
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showed that adding eight cycles to the PCR program for the real-time
Salmonella
assay minimizes the risk
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of a false negative result for samples at or near the limit of detection, and slightly increases the method’s
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sensitivity.
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All components of the certified method remain unaltered, including PCR tablet chemistry,
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temperature profile of the PCR and detection process, and all step-by-step instructions for sample
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enrichment and preparation. Moreover, because the real-time
Salmonella
assay already incorporates a
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“hot-start” polymerase and Scorpion™ probe technology, the risk of non-specific product formation, or
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other potentially negative effects from slightly extended PCR, is minimal.
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Several studies were conducted to compare the performance of the updated BAX® System
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method to both the current certified method and the appropriate reference culture methods on a range of
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artificially contaminated matrices. In addition, inclusivity and exclusivity studies were performed to
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demonstrate no significant change in the sensitivity and specificity of the assay.
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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