98 / 596
2
acid sequences,allows for the rapid and specific detection of
Listeria
species in a broad range of
1
food types and environmental surfaces after 24 to 28 hoursof pre-enrichment. After enrichment,
2
samples are evaluated using the 3M MDA 2 -
Listeria
on the 3M
™
Molecular Detection System
3
(MDS). Presumptive positive results are reported in real-time while negative results are
4
displayed after completion of the assay in approximately 75 minutes.
5
Prior to the collaborative study, the 3M MDA 2 -
Listeria
method was validated according to
6
AOAC Guidelines[4] in a harmonized AOAC
®
Performance Tested Method
SM
(PTM) study.
7
The objective of the PTM study was to demonstrate that the 3M MDA 2-
Listeria
method could
8
detect
Listeria
in a broad range of food matrices and environmental surfaces as claimed by the
9
manufacturer. For the 3M MDA 2
- Listeria
PTM evaluation, 13 matrices were evaluated:hot
10
dogs (25g & 125g), salmon (25g), deli turkey (25g & 125g), cottage cheese (25g), vanilla ice
11
cream (25g), queso fresco (25g), spinach (25g), melon (whole), raw chicken leg pieces (25g),
12
raw chicken fillet (25g); concrete (sponge, 225 mL & 100 mL), stainless steel (sponge, 225 mL),
13
and plastic (Enviroswab, 10 mL) environmental samples.
14
Additional PTM parameters (inclusivity, exclusivity, ruggedness, stability and lot-to-lot
15
variability) tested in the PTM studies satisfied the performance requirements for PTM approval.
16
The method was awarded PTM certification number 111501 on November 3
rd
, 2015.
17
The purpose of this collaborative studywas to compare the reproducibility of the 3M MDA 2 -
18
Listeria
method to the United States Department of Agriculture (USDA) Food Safety Inspection
19
Service (FSIS) -Microbiology Laboratory Guidebook (MLG)Chapter 8.09
Isolation and
20
Identification of Listeria monocytogenes from Red Meat, Poultry and Egg Products, and
21
Environmental Samples
[5] for deli turkey (125 g) and raw chicken breast fillet.
22
23
Collaborative Study
24
25
Study Design
26
27
In this collaborative study, two matrices,deli turkeyand raw chicken breast fillet, wereevaluated.
28
The matrices were obtained from a local retailer and screened for the presenceof
Listeria
by the
29
USDA/FSIS MLG 8.09 reference method
.
The raw chicken breast fillet was artificially
30
contaminated with fresh unstressed cells of
Listeria monocytogenes
, American Type Culture
31
Collection (ATCC) 7644, and the deli turkeywas artificially contaminated with heat stressed
32
cells of
Listeria monocytogenes
,ATCC 19115,at two inoculation levels: a high inoculation level
33
of approximately 2-5 colony-forming units (CFU)/test portion and a low inoculation level of
34
approximately 0.2-2 CFU/test portion. A set of un-inoculated control test portions (0 CFU/test
35
portion) were also included.
36
Twelve replicate samples from each of the three inoculation levels were analyzed by each
37
method. Two sets of samples (72 total) were sent to each laboratory for analysis by 3M MDA 2 -
38
Listeria
and the USDA/FSIS MLG Chapter 8.09 reference method due to the different sample
39
enrichment procedures for each method. Additionally, collaborators were sent a 60 g test portion
40
and instructed to conduct atotal aerobic plate count (APC) using 3M
™
Petrifilm™Rapid Aerobic
41
Count Plate (AOAC Official Method 2015.13) [6] on the day samples were received for the
42
purpose of determining the total aerobic microbial load.
43
A detailed collaborative study packet outlining all necessary information related to the study
44
including media preparation, test portion preparation and documentation of results was sent to
45
each collaborating laboratory prior to the initiation of the study. A conference call was then
46
conducted to discuss the details of the collaborative study packet and answer any questions from
47
the participating laboratories.
48
49
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-29 A/ Collaboartive Study Manuscript
OMA ERP June 2016
ERP Use Only