C
rowley
et al
.
:
J
ournal of
AOAC I
nternational
V
ol
.
95, N
o
. 5, 2012
1429
is not recognized, the system will suggest supplemental tests
to distinguish between two or three closely related organisms,
or indicate the result as an unidentified organism (either >3
organisms can exhibit the observed pattern, or the biopattern
is very atypical and is not represented in the database). It
is recommended that hemolysis on blood agar is reviewed
for any identification of
Listeria innocua.
If
b
-hemolysis is
observed, further testing must be performed to exclude
Listeria
monocytogenes.
Reference:
J. AOAC Int.
95
, 1427(2012)
Results
In the collaborative study, a total of 720 isolates were analyzed
representing 12 different inclusivity species and 120 isolates
screened representing six different exclusivity species. Twenty
laboratories representing government, industry, and private
testing laboratories throughout the United States participated.
The individual isolate results for both inclusivity and exclusivity
reported by each laboratory are presented in Tables 3 and 4,
respectively. Tables
2011.02A
and
2011.02B
present a summary
of the collaborative study including the number of isolates
identified correctly, misidentified, unidentified, or not tested.
For the purposes of this collaborative study, an unidentified or
misidentified isolate was considered a missed identification.
Discussion
Inclusivity
For the inclusivity evaluation, each laboratory identified
isolates from CBA, TSA, and TSAB subculture media for each
of the 12 claimed species. All of the collaborators completed all
of the isolates submitted. A total of 714 strains were identified
correctly by theVITEK 2 GPmethod. Six isolates were not tested
by the VITEK 2 GP method due to being excluded by Gram
stain reactions. For
L. innocua
, Laboratory 3 reported a low
discrimination between
L. innocua
and
L.
welshimeri
on TSA
only. Laboratories 2, 3, 11, and 13 reported low discrimination
between
L.
seeligeri, L. ivanovii,
and
L. welshimeri
on either
CBA or TSAB for
L. seeligeri
. Laboratories 6, 10, 11, and
14 reported low discrimination between
L. innocua
and
L. welshimeri
for
L. welshimeri
on TSA or TSAB. Laboratories
10, 11, and 18 reported low discrimination between
S. aureus
and
S. intermedius
for
S. aureus
on TSAB only. As indicated
in the VITEK 2 GP method, a low discrimination result
is considered a correct identification. Supplemental tests
recommended on the result printout were conducted to provide
a correct final identification of the species. There were zero
isolates that produced a misidentified or an unidentified result
for the inclusivity panel.
Exclusivity
For the exclusivity evaluation, each laboratory received
six nontarget species that consisted of three Gram-negative
bacteria, one
Bacillus
, one yeast, and one mold. All of the
collaborators completed all of the isolates submitted. Of the
120 isolates screened, 106 were correctly excluded. A total of
14 isolates were incorrectly characterized as a Gram-positive
organism resulting in improper analysis and misidentification
by VITEK 2 GP. Laboratories 1, 2, 5, 7, 8, 10, 11, 15, and
18 characterized
B. coagulans
as a Gram-positive or a Gram-
positive with endospores and resulted in an Unidentified
Organism reported by the VITEK 2 GP method. This is
due to the fact that Bacilli are not covered in the scope of
the VITEK 2 GP test system. Laboratory 13 characterized
B. coagulans
as Gram-positive cocci and reported the
VITEK 2 GP results as
Streptococcus mitis
. Laboratories 10 and
14 characterized
Escherichia coli
as a Gram-positive organism
and reported the VITEK 2 identification as Unidentified
Organism. Laboratories 1 and 8 incorrectly characterized
Candida albicans
as a Gram-positive organism and reported
the VITEK 2 identification as
Kocuria varians
.
Recommendations
It is recommended that the VITEK 2 GP test card method be
adopted as Official First Action for the identification of selected
Gram-positive bacterium.
Acknowledgements
We would like to extend a sincere thank you to the following
collaborators for their dedicated participation in this study:
John Mills, Judith Colón-Reveles, and Hari P. Dwivedi,
bioMérieux Industry, Hazelwood, MO
Yvonne Salfinger, Sun Kim, Patricia Hanson, and Jason
Crowe, Florida Department of Agriculture and Consumer
Services, Tallahassee, FL
Tom Sidebottom and Carol Elems, FDA San Francisco
District Office, Alameda, CA
Maureen Coakley, Jennifer Canale, and Gloria Parra, FDA
Northeast Regional Laboratory, Jamaica, NY
Sung Guk Kim and Latriana Robertson, FDANational Center
for Toxicological Research, Jefferson, AR
Hua Wang, FDA Center for Food Safety and Applied
Nutrition, College Park, MD
Leeann Johnson and Bryanne Shaw, Minnesota Department
of Agriculture, St. Paul, MN
Denise Toney and Marta Segarra, Division of Consolidated
Laboratory Services, Richmond, VA
Debra Cherney and Joanne Ruebl, Cherney Microbiological
Services, Ltd, Green Bay, WI
Melinda Hayman, April Garza, and Sergio Montez, Food
Safety Net Services, Ltd, San Antonio, TX
Jayne Finnigan and Peter Wikoff, New Hampshire Public
Health Laboratories Food Safety Micro/Rabies Unit, Concord,
NH
Pete Dombroski, Illinois Department of Public Health
Laboratory Springfield Combined Laboratory Facility,
Springfield, IL
Mary Ann Murphy, Jackie Glover, and Rebecca Daugherty,
U.S. Department of Agriculture-Agricultural Marketing
Service, National Science Laboratory, Gastonia, NC
Karen Wilson and Sheri Robeson, Michigan Department of
Agriculture, Lansing, MI
Adam Miller, Rhode Island Department of Health
Laboratories, Providence, RI
Jessica Dyer and Urvashi Patel, North Carolina Department
of Agriculture, Food and Drug Protection Division, Raleigh, NC
Candidates for 2016 Method of the Year
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