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using the biochemical and serological methods described in the FDA-BAM. Additionally, an MPN
283
was determined using 3 X 100g, 3 X 10g and 3 X 1g samples on the day of testing along with the
284
25 X 20 spiked samples tested using the reference method. The additional samples were treated
285
in an analogous manner to the reference method samples diluted 1:10 in LB enrichment media.
286
An aerobic plate count (APC) on un-spiked material was conducted on the day enrichment
287
commenced.
288
Twenty spiked and five unspiked samples for the test method were enriched at 39-42°C in BAX®
289
System MP media (without pH adjustment) that had been pre-warmed (to incubation temperature)
290
for 24 hours and tested by BAX® System assay at 12 and 24 hours before secondary enrichment
291
in RV and TT broth as for reference method enriched samples. All samples were then struck in 10-
292
μL amounts on BS agar, XLD agar and HE agar. Agars were incubated at 35°C for 24±2 hr after
293
which plates were examined for colonies with typical characteristics of
Salmonella
. Suspect
294
colonies were confirmed using the biochemical and serological methods described in the FDA-
295
BAM.
296
297
Lettuce (Romaine Bagged)
– A master sample was made at ~ 2 cfu per analytical portion.
298
Lettuce was divided into portions of analytical size (25g) and each inoculated with 4 X 10µL
299
aliquots of an approximately 2 cfu / 40µL suspension. The lettuce portions were re-combined in a
300
large bag and mixed thoroughly by shaking. The lettuce was held at 4±3°C for two days to three
301
days to acclimate/stress the target cells. Analytical size portions (25g) were removed and placed
302
into sterile stomacher bags.
303
Twenty inoculated and five un-inoculated lettuce samples tested with the reference method were
304
mixed in 225 mL of LB (BAM method). Contents were swirled and allowed to sit at 25ºC for
305
60
±
5min. The pH was adjusted to 6.8
±
0.2, if necessary, and samples incubated at 35±2°C for
306
24
±
2 hr. Additionally, an MPN was conducted using 3 X 100g, 3 X 10g and 3 X 1g samples on the
307
day of testing. These samples were treated in an analogous manner to the reference method
308
diluted 1:10 in LB enrichment media. An aerobic plate count (APC) on un-spiked material was also
309
conducted on the day enrichment commenced. Enriched samples were added in 0.1-mL aliquots
310
Dupont BAX Salmonella PTM Report
PTM Certification No. 081201 (08/07/2012)
For Expert Review Panel Use Only
Do Not Distribute