273 / 1195
AOAC INTERNATIONAL
and subjected to a 3-hour regrowth; Chi-square and POD calculations demonstrate that
500
this difference is not statistically significant. All BAX® System results were confirmed by
501
the culture method, with the exception of one BAX® System positive result for an
502
environmental sample enriched in BPW and subjected to a 3-hour regrowth before
503
testing. Because this result was a low-level positive, and could not be culture confirmed,
504
it is possible that this result is the result of a cross contamination event but it could also
505
be the result of high levels of the co-inoculated contaminating organism (
Citrobacter
506
brakii
) outcompeting the target and preventing culture confirmation.
507
The results for samples tested by the independent laboratory are also summarized in
508
the tables above. For cream cheese samples, analysis by POD and Chi-square
509
demonstrate that the difference in results between the two methods (14/20 positive for
510
the BAX® System method and 10/20 for the reference method) was not statistically
511
significant. For environmental samples, the BAX® System returned results identical to
512
the reference culture method.
513
514
515
17. LOT-TO-LOT AND STABILITY STUDY
516
517
Methodology
– BAX® System Real-Time
Salmonella
test kits from three lots with different
518
expiration dates were evaluated in experiments to establish lot-to-lot consistency and
519
determine a reasonable shelf-life using both accelerated and non-accelerated storage
520
conditions (see Table 4 below). One
Salmonella
strain was assayed ten times per time
521
point per test kit using cells diluted to one order of magnitude over the product’s claimed
522
sensitivity level (i.e. 10
5
cfu/mL) by the BAX® System assay. Additionally, one non-target
523
strain was tested six times per strain per time point diluted to 10
8
cfu/mL. Also, for each
524
condition, for each time point, two non-spiked lysis buffer controls were tested.
525
Based on these results and applying the Q
10
rule of the Arrhenius equation, a four year
526
shelf life would be supported.
527
Predicted Stability = Accelerated Stability X 2
∆
t/10
528
529
In this case: Stability of a product at 37°C is > 147 days.
530
Recommended storage temperature is 4°C and n = (37 - 4)/10 = 3.3
531
Dupont BAX Salmonella PTM Report
PTM Certification No. 081201 (08/07/2012)
For Expert Review Panel Use Only
Do Not Distribute