4. AOACRIMicroMethods-2018Awards

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C rowley et al .: J ournal of AOAC I nternational V ol . 97, N o . 2, 2014  435

Table 2013.10B. Summary of results for the detection of Listeria spp. in queso fresco (125 g) Method a VIDAS LPT w/OXA

VIDAS LPT w/ALOA

Inoculation level

Uninoculated

Low

High Uninoculated

Low

High

Candidate presumptive positive/total No. of samples analyzed

0/144

70/144

144/144

0/144

70/144

144/144

Candidate presumptive POD (CP)

0.00

0.49

1.00

0.00

0.49

1.00

(0.00, 0.03)

(0.40, 0.57) (0.97, 1.00)

(0.00, 0.03) (0.40, 0.57)

(0.97, 1.00)

b

0.00

0.51

0.00

0.00

0.51

0.00

s r

(0.00, 0.16)

(0.46, 0.52) (0.00, 0.16)

(0.00, 0.16) (0.46, 0.52)

(0.00, 0.16)

c

0.00

0.00

0.00

0.00

0.00

0.00

s L

(0.00, 0.16)

(0.00, 0.12) (0.00, 0.16)

(0.00, 0.16) (0.00, 0.12)

(0.00, 0.16)

d

0.00

0.51

0.00

0.00

0.51

0.00

s R

(0.00, 0.22)

(0.46, 0.52) (0.00, 0.22)

(0.00, 0.22) (0.46, 0.52)

(0.00, 0.22)

P value e

1.0000

0.9730

1.0000

1.0000

0.9730

1.0000

Candidate confirmed positive/total No. of samples analyzed

0/144

70/144

144/144

0/144

70/144

144/144

Candidate confirmed POD (CC)

0.00

0.49

1.00

0.00

0.49

1.00

(0.00, 0.03)

(0.40, 0.57) (0.97, 1.00)

(0.00, 0.03) (0.40, 0.57)

(0.97, 1.00)

0.00

0.51

0.00

0.00

0.51

0.00

s r

(0.00, 0.16)

(0.46, 0.52) (0.00, 0.16)

(0.00, 0.16) (0.46, 0.52)

(0.00, 0.16)

0.00

0.00

0.00

0.00

0.00

0.00

s L

(0.00, 0.16)

(0.00, 0.12) (0.00, 0.16)

(0.00, 0.16) (0.00, 0.12)

(0.00, 0.16)

0.00

0.51

0.00

0.00

0.51

0.00

s R

(0.00, 0.22)

(0.46, 0.52) (0.00, 0.22)

(0.00, 0.22) (0.46, 0.52)

(0.00, 0.22)

P value

1.0000

0.9730 69/144

1.0000 144/144

1.0000

0.9730 69/144

1.0000 144/144

Positive reference samples/total No. of samples analyzed

0/144

0/144

Reference POD

0.00

0.48

1.00

0.00

0.48

1.00

(0.00, 0.03)

(0.39, 0.56) (0.97, 1.00)

(0.00, 0.03) (0.39, 0.56)

(0.97, 1.00)

0.00

0.51

0.00

0.00

0.51

0.00

s r

(0.00, 0.16)

(0.46, 0.52) (0.00, 0.16)

(0.00, 0.16) (0.46, 0.52)

(0.00, 0.16)

0.00

0.00

0.00

0.00

0.00

0.00

s L

(0.00, 0.16)

(0.00, 0.12) (0.00, 0.16)

(0.00, 0.16) (0.00, 0.12)

(0.00, 0.16)

0.00

0.51

0.00

0.00

0.51

0.00

s R

(0.00, 0.22)

(0.46, 0.52) (0.00, 0.22)

(0.00, 0.22) (0.46, 0.52)

(0.00, 0.22)

P value

1.0000

0.9672

1.0000

1.0000

0.9672

1.0000

dLPOD (C vs R)

0.00

0.01

0.00

0.00

0.01

0.00

(–0.03, 0.03)

(–0.10, 0.13) (–0.03, 0.03) (–0.03, 0.03) (–0.10, 0.13) (–0.03, 0.03)

dLPOD (CP vs CC)

0.00

0.00

0.00

0.00

0.00

0.00

(–0.03, 0.03)

(–0.12, 0.12) (–0.03, 0.03) (–0.03, 0.03) (–0.12, 0.12) (–0.03, 0.03)

a Results include 95% confidence intervals. b Repeatability standard deviation. c Among-laboratory standard deviation. d Reproducibility standard deviation. e  P value = Homogeneity test of laboratory PODs.

strips. All of the assay steps are performed automatically by the instrument. The reaction medium is cycled in and out of the SPR several times. An aliquot of enrichment broth is dispensed into the reagent strip. The Listeria receptors present will bind to the interior of the SPR. Unbound components are eliminated during the washing steps. The proteins conjugated 03/10/2019

to the alkaline phosphatase are cycled in and out of the SPR and will bind to any Listeria receptors, which are themselves bound to the SPR wall. A final wash step removes unbound conjugate. During the final detection step, the substrate (4-methyl-umbelliferyl phosphate) is cycled in and out of the SPR. The conjugate enzyme catalyzes the hydrolysis of the