AOAC ERP MICRO AUGUST 2018

OMAMAN-30 D/ PTM Validation Report 081501 OMA ERP - June 2016 ERP Use Only

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Internal Study

Inclusivity and Exclusivity

Methodology

Fifty frozen Listeriamonocytogenes strainsusp ensions were thawed and sub-cultured in brain heart infusion (BHI) broth overnight at 37°C ± 1°C. The cultures were diluted in peptone salt solution in order to inoculate between 10 to 100 cells per 225 mL of Demi Fraser. The enrichment broths were incubated for 24 hours at 37°C ± 1°C, and the3M MDA2 - Thirty frozen non- Listeriamonocytogenes strain suspensions were thawed and sub-cultured grown in BHI broth overnight at 37°C ± 1°C. The cultures were diluted in buffered peptone water (BPW) or de Man, Rogosa, and Sharpe (MRS) in order to inoculate 10 5 cells/mL.The broths were then incubated for 24 hours at the appropriate incubation temperature in order to have Listeriamonocytogenes method wasthen performed.

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culture to test with the 3M MDA2 – Listeriamonocytogenes method.

Results

All 50 Listeriamonocytogenes strains were detected by the 3M MDA2 - Listeriamonocytogenes method. None of the 30 non- Listeriamonocytogenes strains were detected.

See Tables 2 and 3 for study details and results.

Matrix Study

The matrix study consisted of evaluating a total of 30 un-paired sample replicates for 11 matrices, along with a raw chicken leg pieces evaluating 20 sample replicates using two separate lots. Within each sample set, there were 5 uninoculated samples (0 CFU/test portion), 20 low level inoculated samples (0.2-2 CFU/test portion), and 5 high level inoculated samples (2-5 CFU/test portion), except for raw chicken leg pieces that were naturally contaminated with the target analyte. The inoculum was prepared by transferring a single Listeriamonocytogenes colony from Trypticase soy agar with 5% sheep blood (SBA) into BHI broth and incubating the culture at 35 ± 2 o C for 24 ± 2 hours. Table 4 presents the sample preparation guidelines for the matrix. All matrices were screened for the presence of the target organism following the appropriate reference method. Additionally, an aerobic plate count (APC) was conducted following the FDA/BAM Chapter 3 reference [9] method to determine the level of background flora in each Prior to inoculation of beef hot dogs, deli turkey, and queso fresco the broth culture inoculum was heat stressed for 10 ± 1 minute at 50 ± 1°C in a water bath. The degree of injury of the culture was estimated by plating an aliquot of diluted culture onto modified Oxford agar (MOX) and Tryptic Soy agar (TSA). The agars were incubated at 35 ± 1°C for 24 ± 2 hours and the test matrix prior to inoculation.

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colonies were counted. The degree of injury was estimated as:

n

1(

100 )

x

select

−

n

44 45

nonselect