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H.
Confirmation
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All test method samples, regardless of presumptive result, were confirmed by culture and the
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biochemical and serological protocols described in U.S. FDA Bacteriological Analytical Manual (FDA-
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BAM) Chapter 5, USDA-FSIS Microbiology Laboratory Guidebook (MLG) Chapter 4.05, and/or Health
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Canada Compendium of Analytical Methods MFHPB-20, using the appropriate confirmation media, B(o).
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Results and Discussion
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Note: All results are described for samples taken at the longest enrichment time point. Unless otherwise
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noted, each matrix returned identical results at each time point tested (data provided upon request).
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The results for meat and seafood samples are summarized in Tables 4 and 5. For each sample type, the
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BAX® System method and the reference methods demonstrated no significant statistical difference as
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indicated by POD analysis (the 95% confidence interval of the dPOD included 0 in all cases).
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The results for poultry and egg samples are summarized in Tables 6 and 7. For each sample type, the
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BAX® System method and the reference methods demonstrated no significant statistical difference as
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indicated by POD analysis (the 95% confidence interval of the dPOD included 0 in all cases).
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The results for produce samples are summarized in Tables 8 and 9. For each sample type, the BAX®
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System method and the reference methods demonstrated no significant statistical difference as
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indicated by POD analysis (the 95% confidence interval of the dPOD included 0 in all cases).
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The results for dairy product samples are summarized in Tables 10 and 11. For each sample type, the
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BAX® System method and the reference methods demonstrated no significant statistical difference as
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indicated by POD analysis (the 95% confidence interval of the dPOD included 0 in all cases).
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The results for environmental samples are summarized in Tables 12 and 13. For each sample type, the
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BAX® System method and the reference methods demonstrated no significant statistical difference as
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indicated by POD analysis (the 95% confidence interval of the dPOD included 0 in all cases).
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The results for the remaining sample types evaluated are summarized in Tables 14 and 15. For each
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sample type, the BAX® System method and the reference methods demonstrated no significant
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statistical difference as indicated by POD analysis (the 95% confidence interval of the dPOD included 0 in
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all cases). One finding from this study is that
Salmonella
will reliably grow from cocoa enrichments to
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relatively high cell densities, which allow for a dilution to remove PCR inhibitors without a three-hour
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regrowth time. Though this may not be applicable to all chocolate matrix variants, this option allows for
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a reduced time to result for this matrix.
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Overall, the DuPont™ BAX® System Real-time PCR Assay for
Salmonella
demonstrates accuracy and
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reliability statistically equivalent to the reference culture methods used in this study, with a number of
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additional benefits. Due to the greater robustness of this new PCR assay in the presence of PCR
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inhibitors, the test method no longer requires a three-hour re-growth step for many matrices (with the
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exception of some plant-based food items). For many matrices, re-growth was validated as an optional
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step to allow for validated methods in cases where PCR inhibitors may be present in a variant of a matrix
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Dupont BAX Salmonella Pre- Collaborative Study
For Expert Review Panel Use Only
Do Not Distribute
AOAC INTERNATIONAL