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.
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ournal of
AOAC I
nternational
V
ol
. 95, N
o
. 5, 2012
(
d
) Store VITEK 2 GP cards at 2–8°C.
(
e
) Do not freeze test cards.
(
f
) Bring reagents to room temperature before inserting them
into the VITEK 2 instrument.
(
g
) Return unused cards to 2–8°C immediately after use.
Note
: A Gram stain should be performed to determine a pure
culture’s Gram reaction and morphology prior to selecting which
VITEK 2 identification card to inoculate. Interpretation of test
results requires the judgment and skill of a person proficient in
Gram staining and knowledgeable in the interpretation of the
Gram reaction and morphology of microorganisms.
D. Preparation of Test Suspension
(
a
) Aseptically transfer 3.0 mL sterile saline (aqueous
0.45 to 0.50% NaCl, pH 4.5–7.0) into polystyrene test tubes
(12×75 mm). Do not use glass tubes.
(
b
) Using a sterile stick or swab, transfer a sufficient number
of colonies from a 24 h culture on recommended culture medium
to the saline tube to achieve a density equivalent to McFarland
0.50 to 0.63 with the VITEK 2 DENSICHEK.
(
c
) Test the cultures by the VITEK 2 GP method within
30 min of preparation of the suspended culture.
(
d
) Insert the culture tube and the VITEK 2 GP card into the
VITEK 2 cassette and refer to the User Manual (to be provided
with the instrument) for instructions on use of the instrument.
(
e
) Report identification results from the VITEK 2 system.
(
f
) As indicated in the VITEK 2 GP product information
provided to end-users, slashline or low discrimination
identifications are acceptable results for the VITEK 2 GP
method that require supplemental tests to further resolve the
organism identification.
E. Results and Interpretation
The results are interpreted by the VITEK 2 system. Printed
results will indicate a high probability match to a single species if
a unique identification pattern is recognized. If a unique pattern
Table 2012.02B. Interlaboratory study results for the
VITEK 2 GP identification method: Exclusivity isolates
Organism
Misidentified
a
Unidentified
b
Not
tested
c
Total
d
Bacillus coagulans
3
27
10
40
Citrobacter freundii
0
0
20
20
Escherichia coli
0
6
14
20
Serratia marcescens
0
0
20
20
Aspergillus niger
0
0
20
20
Candida albicans
6
0
14
20
Total Isolates
9
e
33
e
98 140
a
Organism was incorrectly characterized by Gram stain and was
improperly tested by the VITEK 2 GP method resulting in misidentifi-
cation.
b
Organism was incorrectly characterized by Gram stain and was
improperly tested by the VITEK 2 GP method resulting in no identifica-
tion.
c
Organism was excluded by Gram stain procedure and was not tested
on VITEK 2 GP card as per protocol.
d
Total numbers represent each strain not tested and strains that were
misidentified and unidentified.
e
Total number of isolates incorrectly tested by the VITEK 2 GP method
after erroneous Gram stain result.
Table 2012.02C. Biochemical tests included in the VITEK
2 GP card
Well
Test
Abbreviation
2
D-Amygdalin
AMY
4
Phosphatidylinositol phospholipase C
PIPLC
5
D-Xylose
dXYL
8
Arginine Dihydrolase 1
ADH1
9
b
-Galactosidase
BGAL
11
a
-Glucosidase
AGLU
13
Ala Phe Pro arylamidase
APPA
14
Cyclodextrin
CDEX
15
L-Aspartate arylamidase
AspA
16
b
Galactopyranosidase
BGAR
17
a
-Mannosidase
AMAN
19
Phosphatase
PHOS
20
Leucine arylamidase
LeuA
23
L-Proline arylamidase
ProA
24
b
-Glucaronidase
BGURr
25
a
-Galactosidase
AGAL
26
L-Pyrrolidonyl-arylamidase
PyrA
27
b
-Glucaronidase
BGUR
28
Alanine arylamidase
AlaA
29
Tyrosine arylamidase
TyrA
30
D-Sorbitol
dSOR
31
Urease
URE
32
Polymixin B resistance
POLYB
37
D-Galactose
dGAL
38
D-Ribose
dRIB
39
L-Lactate alkalinization
ILATk
42
Lactose
LAC
44
N
-Acetyl-D-glucosamine
NAG
45
D-Maltose
dMAL
46
Bacitracin resistance
BACI
47
Novobiocin resistance
NOVO
50
Growth in 6.5% NaCl
NC6.5
52
D-Mannitol
dMAN
53
D-Mannose
dMNE
54
Methyl-B-D-glucopyranoside
MBdG
56
Pullulan
PUL
57
D-Raffinose
dRAF
58
O/129 Resistance (comp.vibrio.)
O129R
59
Salicin
SAL
60
Saccharose/sucrose
SAC
62
D-Trehalose
dTRE
63
Arginine dihydrolase 2
ADH2s
64
Optochin resistance
OPTO
Candidates for 2016 Method of the Year
264