226 / 1195
AOAC INTERNATIONAL
an assumed concentration of 10
9
cfu/mL. Strains were serially diluted in additional BHI broth to levels
182
expected to produce fractional positive results based on previous studies.
183
184
Table 1. Selected Matrices and Enrichment Methods
Sample
matrix
Inoculation strain
name and ID
BAX® System enrichment media Reference method
Reference method
enrichment media
Ground
Beef
S.Heidelberg
(
DD13017
)
mTSB (TSB + 2 mg/L novobiocin)
USDA MLG [4]
BPW* / TT-Hajna & RVS
mTSB (TSB + 2 mg/L novobiocin) Health Canada [3]
BPW / TBG & RVS
Cream
Cheese
S
. Typhimurium
(DD586)
BAX® System MP media
U.S. FDA BAM [2]
LB* / FDA RV & TT
Dry Pet
Food
S
. Tennessee
(DD13062)
BPW / BHI broth
Health Canada [3]
BPW / TBG & RVS
Lactose broth / BHI broth
Health Canada [3]
BPW / TBG & RVS
* Reference method enrichment schemes also evaluated with the BAX® System test method.
185
186
For ground beef, a master sample was made at approximately 1 cfu per analytical portion. Ground
187
beef was divided into portions of reference method analytical size (25g) and each was inoculated with
188
4 X 10µL aliquots of an approximately 1 cfu / 40 µL suspension. Some portions were left un-spiked to
189
serve as negative controls. Spiked ground beef portions were re-combined on an aluminum foil coated
190
surface and hand massaged to homogenize. The master sample was held at 4±3°C for two to three
191
days to acclimate/stress the target cells. For the reference methods, analytical size portions (25 g)
192
were placed into sterile bags. For the BAX® System method, analytical size portions (25 g spiked
193
master sample and 350 g of unspiked product for each sample) were placed into sterile bags.
194
For cream cheese, a master sample was made at approximately 1 cfu per analytical portion.
195
Cream cheese was divided into portions of analytical size (25 g) and each was inoculated with 4 X 10
196
µL aliquots of an approximately 1 cfu / 40 µL suspension. Some portions were left un-spiked to serve
197
as negative controls. Spiked cream cheese portions were re-combined on an aluminum foil coated
198
surface and hand massaged to homogenize, then all test portions were held at 2-8°C for two to three
199
days to acclimate/stress the target cells. Analytical size portions (25 g) were removed and placed into
200
sterile stomacher bags.
201
Dupont BAX Salmonella PTM Report
Modification Approved 2012 / PTM Certification No. 081201
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