AOAC RI ERP Final Action Recommendations eBook

Dupont BAX Salmonella PTM Report Modification Approved 2012 / PTM Certification No. 081201 For Expert Review Panel Use Only Do Not Distribute

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an assumed concentration of 10 9 cfu/mL. Strains were serially diluted in additional BHI broth to levels

expected to produce fractional positive results based on previous studies.

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Table 1. Selected Matrices and Enrichment Methods Sample matrix Inoculation strain name and ID

Reference method enrichment media

BAX® System enrichment media Reference method

Ground Beef

S.Heidelberg ( DD13017 )

USDA MLG [4]

mTSB (TSB + 2 mg/L novobiocin)

BPW* / TT-Hajna & RVS

mTSB (TSB + 2 mg/L novobiocin) Health Canada [3]

BPW / TBG & RVS

Cream Cheese Dry Pet Food

S . Typhimurium (DD586) S . Tennessee (DD13062)

BAX® System MP media

U.S. FDA BAM [2]

LB* / FDA RV & TT

BPW / BHI broth

Health Canada [3]

BPW / TBG & RVS

Lactose broth / BHI broth

Health Canada [3]

BPW / TBG & RVS

185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201

* Reference method enrichment schemes also evaluated with the BAX® System test method.

For ground beef, a master sample was made at approximately 1 cfu per analytical portion. Ground

beef was divided into portions of reference method analytical size (25g) and each was inoculated with

4 X 10µL aliquots of an approximately 1 cfu / 40 µL suspension. Some portions were left un-spiked to

serve as negative controls. Spiked ground beef portions were re-combined on an aluminum foil coated

surface and hand massaged to homogenize. The master sample was held at 4±3°C for two to three

days to acclimate/stress the target cells. For the reference methods, analytical size portions (25 g)

were placed into sterile bags. For the BAX® System method, analytical size portions (25 g spiked

master sample and 350 g of unspiked product for each sample) were placed into sterile bags.

For cream cheese, a master sample was made at approximately 1 cfu per analytical portion.

AOAC INTERNATIONAL Cream cheese was divided into portions of analytical size (25 g) and each was inoculated with 4 X 10 µL aliquots of an approximately 1 cfu / 40 µL suspension. Some portions were left un-spiked to serve as negative controls. Spiked cream cheese portions were re-combined on an aluminum foil coated

surface and hand massaged to homogenize, then all test portions were held at 2-8°C for two to three

days to acclimate/stress the target cells. Analytical size portions (25 g) were removed and placed into

sterile stomacher bags.