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- Inclusivity:
The strains or isolates of the target analyte(s) that the method
can detect.
- Exclusivity
:
The non-target strains or isolates, which are potentially cross-
reactive, that should not be detected by the method.
General Information
Most
E. coli
bacteria are harmless; however some produce a toxin (Shiga toxin) that can
cause serious illness, including bloody diarrhea, hemolytic uremic syndrome, renal failure,
and sometimes death. Like generic
E. coli
, toxin-producing Shiga-toxigenic
E. coli
(STEC)
are Gram-negative, rod-shaped bacteria, but are characterized by the production of Shiga
toxins (
stx1, stx2)
and
eae
. Depending on the reference cited, there are approximately 200
to 400 STEC serotypes, many of which have not been implicated in human illness;
however, a subset of STEC called enterohemorrhagic
Escherichia coli
(EHEC) includes
only those that cause serious illness. Serotype O157:H7 is the prototypic EHEC strain.
Although
E. coli
O157:H7 is currently the predominant strain and accounts for ~75% of the
EHEC infections worldwide, other non-O157 EHEC serotypes are emerging as a cause of
foodborne illnesses. In the United States the group known as the “Top 6” or “Big 6” (O111,
O26, O121, O103, O145, and O45) accounts for the majority of non-O157:H7 serotypes
isolated from clinical infections and, therefore, is currently a focus of concern.
EHEC outbreaks have been traced to many differenttypes of foods such asraw ground
meats, unpasteurized (“raw”) milk, unpasteurized fruit juice, lettuce, spinach, sprouts,
andmore recently, commercially manufactured frozen cookie dough. EHEC infections can
lead to life-threatening complications with children and immuno-compromised individuals
being at especially high risk. Thorough cooking of ground beef; washing raw fruits and
vegetables under clean, running water; and not drinking unpasteurized (“raw”) milk or
eating certain cheeses made from raw milk will decrease the chance of foodborne
illness.[4]
Principle of the Method
QIAGEN’s
mericon
E.coliO157 Screen Plus and
mericon
E.coliSTEC O-TypePathogen
Detection Assays are multiplex PCR assays that amplify both a specific DNA target and an
internal control with high specificity. The internal control provides data regarding the
presence of inhibitors in the tested samples and the overall quality of the PCR
run. Each
mericon
PCR Assay includes a PCR primer set for a pathogen-specific target
sequence, probes labeled with four distinct fluorescent dyes (
mericon
E. coliO157 Screen
Plus) or three distinct fluorescent dyes (
mericon
E. coliSTEC O-Type), positive control
DNA, and all of the reagents necessary to perform the analysis. The Multiplex PCR Master
Mix included in each kit contains QIAGEN proprietary technology, including
HotStarTaqplus DNApolymerase, patented multiplex PCR technology such as Factor MP,
and fast cycling technology including Q-bond. [5]
The Rotor-Gene Q cycler produces raw data files that are further interpreted by the
software using mathematical algorithms to characterize samples. The software guides the
user through each step and provides simplicity for beginners as well as an experimental
platform for advanced users. [6]
OMAMAN-36 E/ AOAC PTM Report
ERP Use Only
January 2017
AOAC Research Institute
Expert Review Panel Use O ly