AOAC ERP MICRO AUGUST 2018

OMAMAN-44 A: Collaborative Study Manuscript Expert Review Panel Use Only August 2018

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Interpretation and Test Result Report

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( a ) At the end of incubation period, observe plates for colonies viewed through the clear side of

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the Peel Plate ECB. Each colored spot, regardless of color, represents one CFU. The sum of spots is 197

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reported as the Enterobacteriaceae CFU/mL of the diluted sample.

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( 1 ) In the case of cereal, sum the colonies from all 5 plates or count all the colonies on the 5 mL

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plate.

( b ) Multiply CFU/mL by dilution to calculate CFU/mL (or CFU/g) of original sample.

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( 1 ) In the case of cereal, as 5 mL are enumerated, the homogenization dilution is 10 (5mL of 1 to

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50 dilution)

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( 2 ) In the case of surfaces, the count is per mL of buffered used to sample the surface. Multiply

by buffer volume and divide by cm 2 of surface tested to calculate counts/ cm 2 . 205

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( 3 ) In case of poultry rinse, the count is per mL of buffer used to rinse carcass.

( c ) In case of spreading bacteria, score one CFU for each count each dark spot within the spread

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growth as a single colony. Blended colonies are scored as a single CFU.

( d ) Counts of 1 to 154 CFU/mL (or g) are considered countable, while counts outside that range

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are considered estimates. Samples with results outside of countable range (>154 CFU/mL or g) can be 210

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diluted and retested.

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Confirmation The Peel Plate EB method uses selective medium and enzyme substrates to detect ERP Use Only

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Enterobacteriaceae without the need for confirmation steps. While it is not necessary, it may be desired 216

to confirm colonies into traditional selective medium. The cover may be lifted and colonies picked and 217

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