242 / 1195
AOAC INTERNATIONAL
15. INCLUSIVITY EXCLUSIVITY STUDY
387
Sample Preparation and Enrichment
388
For inclusivity testing, 62 different
Salmonella
strains representing more than 50 serotypes
389
were selected from the DuPont Qualicon Culture Collection. These strains originated from a
390
wide range of food, environmental, human and veterinary clinical diagnostic and animal non-
391
diagnostic samples. Cultures were streaked for purity on BHI agar, then one pure colony was
392
inoculated into BPW and incubated at 41°C overnight to reach cell densities of approximately
393
10
9
cfu/ mL. Enrichments were serially diluted to approximately 10
5
cfu/mL before testing, which
394
is 1 log over the claimed sensitivity of the assay.
395
For exclusivity testing, 35 different non-
Salmonella
strains were selected from the DuPont
396
Qualicon Culture Collection. Most of these isolates were selected based upon genetic
397
relatedness to
Salmonella
and originally obtained from naturally contaminated food and food
398
processing environmental samples or from animal sources, and all identifications were
399
confirmed biochemically and/or serologically as appropriate. Exclusivity cultures were primarily
400
selected based upon genetic relatedness to
Salmonella.
Cultures were streaked for purity on
401
BHI agar, then one pure colony was inoculated into a tube containing BHI broth and incubated at
402
35ºC overnight to reach cell densities of approximately 10
9
cfu/ mL. For exclusivity testing,
403
cultures were tested with no dilution.
404
All inclusivity and exclusivity strains were tested with the updated BAX® System method as
405
described above.
406
Results
407
The results of inclusivity testing are displayed in Table 4 below. The updated BAX® System
408
method returned positive results for all 62
Salmonella
strains tested. Compared to the current
409
certified method, which missed one strain,
Salmonella
Westmark II (DD1560), at 10
5
cfu/mL in
410
the original validation study, the updated method shows slightly increased sensitivity and now
411
reliably detects this strain at 10
5
cfu/mL.
412
Dupont BAX Salmonella PTM Report
Modification Approved 2012 / PTM Certification No. 081201
For Expert Review Panel Use Only
Do Not Distribute