231 / 453
19
Subsequently, these samples were screened as negative on the
mericon
E. coliSTEC O-Type
1
assay. These results indicate that these two assays when run in combination, can detect the
2
potential presence of pathogenic genes, but at the same time screen the sample negative for
E.
3
coli
O157 and the Top Six STEC. Additionally, a few of the false positive results obtained had
4
high CT values (>36 CT). These false positive results could be attributed to cross reactivity with
5
background flora that is sometimes observed with matrices with high background counts, or
6
could be the resultof cross contamination from the samples that were inoculated at a high level
7
that were processed prior right before or after the sample. No false negative results were
8
observed for samples analyzed by either assay with manual extraction or with the screening
9
assay and automated extraction. Minimal false negative results (5 false negative results out of
10
432 total samples) were observed for the STEC O-Type assay with automated extraction. Three
11
of the false negative results occurred on a reanalysis of the test sample after the initial sample
12
produced an invalid result (no internal CT value was observed). This may indicate that an error
13
in the sample processing occurred due to the sample containing high levels of particulate. Due to
14
availability of reagents, the reanalysis also occurred several days later, and an increase in
15
background flora may have resulted in the non-detection of the target analyte.
16
17
Recommendations
18
19
It is recommended that the
mericon
E. coliO157Screen Plus and
mericon
E. coliSTEC O-Type
20
method be adopted as Official First Action status for the detection of
E. coli
O157 and the Top
21
Six STEC (
E. coli
O26, O45, O103, O111, O121 and O145 in selected foods: raw ground beef
22
(73%) (325 g), raw beef trim (375 g) and spinach (25 g).
23
24
Acknowledgements
25
26
We would like to extend a sincere thank you to the following collaborators for their dedicated
27
participation in this study:
28
29
Dorn Clark, Michaeline Endres & Kody Guden- Marshfield Food Safety, LLC- Marshfield, WI
30
Leslie Thompson, Cole Liska, Adam Sexton, Eric Draper & Luke Arnts –
31
Vanguard Sciences - North Sioux City, SD
32
Brian Kupski, Upasana Hariram, Jeanette Franklin, Jiaojie Zheng, & Nirlep Kaur –
33
Mérieux NutriSciences – Crete, IL
34
Kyle Matheus - Mérieux NutriSciences – Madison, WI
35
Heidi Wright, Andrew Duss, Andrew Kim & Susan Le– AEMTEK, Inc. – Fremont, CA
36
Allison Mastalerz & Nicole Klass – Microbiology R&D, Q Laboratories Inc., Cincinnati, OH
37
38
We would like to extend a special thanks to the following team members at Q Laboratories, Inc.
39
for their efforts during the collaborative study: Alison DeShields, Dane Brooks, Rebecca Von
40
Handorf, T. Shane Wilson, Jon Clifton, Luke Jett, and Colleen Sweeney.
41
42
We would like to extend special thanks to the members of the QIAGEN Field Service and
43
Logistics teams who ensured that the collaborative study ran smoothly.
44
45
References
46
OMAMAN-36 A : Collaborative Study Manuscript
For ERP Use Only
January 2017
AOAC Research Institute
Expert Review Panel Use Only