ERP Micro December 2019

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uninoculated matrix) test portions and five 130 g (13 g low level inoculated sample plus 117 g uninoculated matrix). For the high inoculation level, use the five 325 g portions as the top level. Include five 130 g (13 g high level inoculated sample plus 117 g uninoculated matrix) and five 50 g (5 g high level inoculated sample plus 45 g uninoculated matrix). Follow MLG 5.09 for testing and confirmation.

3.2.11.33.2.13.3

Access the Least Cost Formulations (LCF) MPN calculator

( 64 ) to determine the MPN values and 95% confidence intervals for the

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bulk inoculated material.

3.3 Matrix Study: Carcass Cloth

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As for food matrices, fractionally positive results, those in which at least one of the methods (candidate or reference) yields 5-15 positive results out of 20 replicates examined, are required for each carcass cloth tested. Results in which the candidate method is above the fractional range and the reference method is below the fractional range are also considered acceptable.

Table 3. Carcass Cloth Sample Preparation

Surface Area (FSIS)

Inoculation Organisms

Inoculation Level

Sampling Device

Type

Replicates

Method

0 cfu

5

Carcass cloth

E. coli O157:H7

MicroTally TM Cloth

280 sq. inch

Assurance IDGDS O157

Low

20

High

5

0 cfu

5

Carcass cloth

E. coli O157:H7

MicroTally TM Cloth

280 sq. inch

MLG 5.095C.00

Low

20

High

5

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3.3.1 The carcass cloth study will include 20 replicate cloths (Fremonta MicroTally TM Manual Sampling Device, MSD, https://www.fremonta.com/microtally ) inoculated at a low level (to achieve fractionally positive results), five replicate cloths inoculated at a high level, and five replicate cloths uninoculated for each method (test method and reference method). Use the Fremonta MicroTally swabs for surface sampling (Table 3). As carcass cloth sample, no MPN analysis

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will be performed.

3.3.2 Grow E. coli O157:H7 to stationary phase in non-selective media at 37 °C.

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