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The sensitivity of both
mericon
assays isequivalent to the FDA/BAM Chapter
4A [1], USDA/FSIS-MLG 5.09 [2], and USDA/FSIS-MLG 5B.05 [3]reference
culture methods. The POD statistical analysis indicated no significant
differences between the
mericon
E.coli O157Screen Plus and
mericon
E.coliSTEC O-TypePathogen Detection Assays, using either the
manual
mericon
DNA extraction orthe automated QIAsymphonyDNA
extraction procedures and the reference methods for all three foodmatrixes
analyzed.Each
mericon
assay correctly identified all 50 target strains analyzed
and correctly excluded all 30 non-target strains analyzed.
Definitions
(a)
Probability of Detection
Probability of Detection (POD) is the proportion of positive analytical
outcomes for a qualitative method for a given matrix at a given analyte level
or concentration. POD is concentration dependent. There are several
POD
measures that can be calculated, e.g., POD
CP
(candidate method
presumptive result POD), POD
CC
(candidate method confirmation result
POD), POD
C
(confirmed candidate method POD), POD
R
(reference method
POD), and dPOD, the difference between any two POD values.
(b)
General Definitions formericonE.coliO157Screen Plus and mericonE.coli
STEC O-TypeAssays
- Ct value:
The cycle threshold value is defined as the number of PCR cycles
required for the fluorescent signal to become significantly different from the
fluorescent background signal. It should be understood that Ct levels are
inversely proportional to the amount of target nucleic acid in the sample (i.e.
the lower the Ct value the greater the amount of target nucleic acid in the
sample).
- Green Channel:
FAM
™
(detection at 495/520 nm wavelength), for the
mericon
E.coliO157
Screen Plus Assay used for the detection of
stx1/stx2
and for the
mericon
E. coli STEC O-Type Assayused to detect the
followingstrains of E. coli:: O26, O45, O103, O111, O121, O145.
- Yellow Channel:
MAX
™
NHS Ester (detection at 524/557 nm wavelength),
for both assays used for the detection of the Internal Control (IC).
- Crimson Channel:
Cy
®
5.5 (detection at 685/707 nm wavelength),for the
mericon
Screen Plus Assay used for the detection of
eae.
- Orange Channel:
ROX
™
NHS Ester (detection at 588/608 nm wavelength),
for the
mericonE. coli O157
Screen Plus Assay used for the detection of
O157and for the
mericon
E. coliSTEC O-Type Assay used for the detection
of O157:H7.
(c)
Other Definitions
OMAMAN-36 E/ AOAC PTM Report
ERP Use Only
January 2017
AOAC Re earch Institute
Expert Review Panel Use Only