4. AOACRIMicroMethods-2018Awards

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440  C rowley et al . : J ournal of AOAC I nternational V ol . 97, N o . 2, 2014

Table 4. Individual collaborator results for queso fresco a (125 g test portions) VIDAS LPT b High-level test portions Low-level test portions

Uninoculated test portions Lab 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 + + + + + + + + + + + + – + + – – – – – + + – + – – – – – – – – – – – – 2 c NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 3 + + + + + + + + + + + + – + + – – – + + – – + + – – – – – – – – – – – – 4 + + + + + + + + + + + + – – – – + – + – + + – + – – – – – – – – – – – – 5 + + + + + + + + + + + + – – + + – – + – – – + + – – – – – – – – – – – – 6 + + + + + + + + + + + + – – + + + – + + – – – – – – – – – – – – – – – – 7 + + + + + + + + + + + + – + – – – + + + – + + + – – – – – – – – – – – – 8 + + + + + + + + + + + + – – + – – + – + + + + + – – – – – – – – – – – – 9 + + + + + + + + + + + + + + + + + – – – – – – – – – – – – – – – – – – – 10 + + + + + + + + + + + + – + + – + + – – + – – + – – – – – – – – – – – – 11 c + + + + + + + + + + + + + + + – – – – – – + – + – – – – – – – – – – – – 12 + + + + + + + + + + + + – + + + + – – + – + + + – – – – – – – – – – – – 13 + + + + + + + + + + + + – – – – – + + + + + – + – – – – – – – – – – – – 14 + + + + + + + + + + + + – – – + + – – + – + – + – – – – – – – – – – – – AOAC 993.12 1 + + + + + + + + + + + + – – – – – + + + + + + + – – – – – – – – – – – – 2 c NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 3 + + + + + + + + + + + + + – – – – + – + – – + + – – – – – – – – – – – – 4 + + + + + + + + + + + + – + – – – + + + + – – + – – – – – – – – – – – – 5 + + + + + + + + + + + + – + + – + – + + – + – + – – – – – – – – – – – – 6 + + + + + + + + + + + + + + – – – + + + – – – – – – – – – – – – – – – – 7 + + + + + + + + + + + + + – – + – + + + – – – – – – – – – – – – – – – – 8 + + + + + + + + + + + + + – + + + + – – + + – – – – – – – – – – – – – – 9 + + + + + + + + + + + + + – – – – + – + – – + – – – – – – – – – – – – – 10 + + + + + + + + + + + + + + – – – + + + – + – – – – – – – – – – – – – – 11 c + + + + + + + + + + + + + d + + e + + + f + f – – + f + + – – + f + e – – – – – + g + g + f 12 + + + + + + + + + + + + + – – – + + – – – + – + – – – – – – – – – – – – 13 + + + + + + + + + + + + + + + + + + – – – – + – – – – – – – – – – – – – 14 + + + + + + + + + + + + – – + – + – – – – + + + – – – – – – – – – – – – a + = Listeria spp. were detected in samples; – = Listeria spp. were not detected in sample; NA laboratory did not participate in this matrix or results were not received. b Confirmed results from OXA and ALOA were identical for each test portion. c Results not used in statistical analysis.

d Result reported as L. welshimeri. e Result reported as L. innocua. f Result reported as L. grayi. g Result reported as L. ivanovii.

the VIDAS LPT assay or the ALOA chromogenic agar. Many laboratories indicated difficulty in identifying and isolating colonies from samples when using OXA plates, but not from test portions analyzed by the VIDAS LPT method. These results may be due to the higher selectivity of the ALOA agar to isolate and differentiate typical Listeria colonies from competing microflora, such as Bacillus colonies. The high selectivity of the proprietary LPT broth, the high background flora, and the low selectivity of the OXA agar most likely contributed to this observation, as well.

agar were identical to the results obtained from the OXA agar specified by AOAC 993.12 . Out of a total of 451 positives detected by the VIDAS LPT, 448 were confirmed positive using OXA or ALOA selective agars.

Discussion

No negative feedback was reported to the study directors from the collaborating laboratories in regards to the performance of 03/10/2019