4. AOACRIMicroMethods-2018Awards

196

1428  C rowley et al . : J ournal of AOAC I nternational V ol . 95, N o . 5, 2012

Table 2012.02B. Interlaboratory study results for the VITEK 2 GP identification method: Exclusivity isolates

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

Not tested c Total d

Misidentified a Unidentified b

Organism

3 0

27

10 20

40 20

Bacillus coagulans Citrobacter freundii

0

0

6

14

20

Escherichia coli

0

0

20

20

Serratia marcescens

0

0

20

20

Aspergillus niger

6

0

14

20

Candida albicans

9 e

33 e

( 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 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. Total Isolates

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