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QIAGEN
mericon
®
E. coliO157 Screen Plusand
mericon
®
E.coli
STEC O-Type Detection Workflows:
AOAC
Performance Tested Methods
SM
101503 and 101504
Abstract
The QIAGEN
mericon
®
E. coli O157 Screen Plus and
mericon
®
E.coliSTEC O-TypePathogen
Detection workflowsemploy Real-Time (RT) PCR technology incorporating a HotStarTaq
DNA Polymerase for the rapid, accurate detection of
Escherichia coli
O157 and non-O157
Shiga toxin-producing
E. coli
STEC(O26, O45, O103, O111, O121, O145)from selected food
products. In this study, both
mericon
workflows were evaluated according to current AOAC
guidelines. The validation consisted of inclusivity, exclusivity, robustness, and a method
comparison study of three food matrixes. The performance of the
mericon
pathogen
detection workflows, using manual and automated DNA extraction procedures, was
compared to Food and Drug Administration Bacteriological Analytical Manual (FDA/BAM)
Chapter 4A:
Diarrheagenic Escherichia coli
for fresh spinach, the United States Department
of Agriculture Food Safety and Inspection Service Microbiology Laboratory Guidebook
(USDA/FSIS-MLG) 5.09:
Detection, Isolation and Identification of Escherichia coli O157:H7
from Meat Products and Carcass and Environmental Sponges
for raw ground beef (70%
lean), or the USDA/FSIS-MLG 5B.05:
Detection and Isolation of non-O157 Shiga Toxin-
Producing Escherichia coli (STEC) from Meat Products and Carcass and Environmental
Sponges
for raw beef trim.
For the inclusivity and exclusivity evaluation, both
mericon
pathogen detection assays
correctly identified all 50 target organism isolates and correctly excluded all 30 non-target
organismsanalyzed.
In the method comparison study, both the
mericon
E.coliScreen PlusAssay and the
mericon
E. coliSTEC O-Type Assay with manual and automated DNA extraction
demonstrated no significant differences between presumptive and confirmed results
(dPOD
CP
) or between candidate and reference method results (dPOD
C
) for all 3 food
matrixesafter 10 hours of enrichment.
Robustness testing demonstrated that minor variations in manual heat lysis time and
sample master mix volume ratios for the
mericon
detection assays did not impact assay
accuracy. The robustness testing did demonstrate that variations in incubation time did
directly impact the assay. Based on the results obtained, it was determined that a minimum
of 10 hours of incubation is needed.
The results of these studies demonstrate adequate sensitivity and selectivity of the
mericon
E.coliO157 Screen Plus and
mericon
E. coliSTEC O-Type Assays with manual and
automated DNA extraction for the detection of
E. coli
O157:H7 and non-O157 STEC
(
O26,
O45, O103, O111, O121, O145
)
in fresh spinach, raw ground beef, and raw beef trim.
OMAMAN-36 E/ AOAC PTM Report
ERP Use Only
January 2017
AOAC Research Institute
Expert Review Panel Use Only