257 / 1195
AOAC INTERNATIONAL
rinse samples may be enriched in 30 mL of either double-strength BPW (if chickens were rinsed in
255
Butterfield’s Phosphate Buffer) or in single-strength BPW if chickens were rinsed in BPW (as was
256
the case in this study).
257
Twenty samples were enriched at 35-36°C in pre-warmed BPW media for 22 hours before transfer
258
for secondary enrichment in TT-Hajna and RVS broths as described in the MLG protocol.
259
Enrichments were tested by BAX® System assay at 16 hours and concurrently with transfer for
260
secondary enrichment.
261
Secondary enrichments for test and reference method samples were struck for isolation on BGS
262
and XLT-4 (USDA) agars. Isolated presumptive
Salmonella
were confirmed as directed in the
263
appropriate corresponding reference methods (biochemical, serological).
264
265
266
Cream Cheese
– A master sample was made at ~ 1 cfu per analytical portion. Two to three days
267
prior to enrichment and assay, cheese was divided into portions of analytical size (25g) and each
268
was inoculated with 4 X 10µL aliquots of an approximately 1 cfu / 40µL suspension. The cheese
269
portions were re-combined on an aluminum foil coated surface and mixed by massage to
270
homogenize and held at 4±3°C for two days to three days to acclimate/stress the target cells.
271
Analytical size portions (25g) were removed and placed into sterile stomacher bags.
272
Twenty inoculated and five un-inoculated cream cheese samples for the reference method were
273
mixed (by stomaching for 2 min at 200 rpm in a sterile Stomacher bag for test method samples
274
and by blending for reference method samples) in 225 mL of LB (BAM method). Contents were
275
swirled and allowed to sit at 25ºC for 60
±
5min. The pH was adjusted to 6.8
±
0.2, if necessary, and
276
samples incubated at 35±2°C for 24
±
2 hr. Enriched samples were added in 0.1-mL aliquots to 10-
277
mL FDA RV broth (prepared from constituent components on the day of testing) and incubated for
278
24
±
2 hr at 42±0.2°C. An additional 1-mL aliquot of each enrichment was added to 10 mL TT broth
279
and incubated for 24
±
2 hr at 35±2°C. All samples were then struck in 10-μL amounts on BS agar,
280
XLD agar and HE agar. Agar plates were incubated at 35°C for 24±2 hr after which, plates were
281
examined for colonies with typical characteristics of
Salmonella
. Suspect colonies were confirmed
282
Dupont BAX Salmonella PTM Report
PTM Certification No. 081201 (08/07/2012)
For Expert Review Panel Use Only
Do Not Distribute