AOAC-RI ERP Book MICRO.pdf

Page

1) Raw Ground Beef (73% lean) (325 gram test portion)

(c) Summary of Validated Performance Claims

The 3M MDA 2 -

E. coli

O157 is considered equivalent to the USDA/FSIS-

MLG 5.09 reference method [1] for the detection of

E. coli

O157 in

raw ground beef (73% lean).

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

(reference method POD), POD

(confirmed candidate method POD), POD

(candidate method presumptive

result POD), POD

(candidate method confirmation result POD) and dPOD,

the difference between any two POD values.

General Information

Most

E. coli

bacteria are harmless; however, some produce a toxin (Shiga toxin) that

can cause serious illness, including bloody diarrhea, hemolytic anemia, renal failure,

and sometimes death. For example, a recent outbreak occurred on February 25, 2016,

by a company called Jack & the Green Sprouts, Inc. recalled all alfalfa and alfalfa onion

sprout products due to nine people infected with the outbreak strain of Shiga toxin-

producing

Escherichia coli

O157 [2]. Like generic

E. coli

, toxin-producing Shiga-

toxigenic

Escherichia coli

(STEC) are Gram-negative, rod-shaped bacteria, but are

characterized by the production of Shiga toxins (

stx

1, stx 2,

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 [3].

Principle of the Method

3M™ Molecular Detection Assay 2 -

E. coli

O157 is used with the 3M™ Molecular

Detection System for the rapid and specific detection of

E. coli

O157 in enriched food

samples. The 3M Molecular Detection Assay uses a loop-mediated isothermal

amplification to rapidly amplify nucleic acid sequences with high specificity and

sensitivity, combined with bioluminescence to detect the amplification. Presumptive

positive results are reported in real-time while negative results are displayed after the

assay is completed. Presumptive positive results should be confirmed using the

appropriate reference method.