4. AOACRIMicroMethods-2018Awards
195
C rowley et al . : J ournal of AOAC I nternational V ol . 95, N o . 5, 2012 1427
Table 2012.02A. Interlaboratory study results for the VITEK 2 GP identification method: Claimed isolates Organism Correct Misidentified Unidentified Not tested a
Total b
60 60
0 0
0 0
0 0
60 60
Listeria grayi
Listeria innocua
Listeria ivanovii ssp. Ivanovii
60
0
0
0
60
Listeria ivanovii ssp. Londoniensis
60
0
0
0
60
60
0
0
0
60
Listeria monocytogenes
57
0
0
3
60
Listeria seeligeri
60
0
0
0
60
Listeria welshimeri
60
0
0
0
60
Staphylococcus hyicus
60
0
0
0
60
Staphylococcus intermedius
60
0
0
0
60
Staphylococcus aureus
57
0
0
3
60
Staphylococcus aureus
60
0
0
0
60
Staphylococcus epidermidis
Total isolates
714
0
0
6
720
a Organism was incorrectly characterized by Gram stain and was not tested on VITEK 2 GP card. b Total numbers represent isolates analyzed on the three recommended culture media: CBA, TSA, and TSAB.
incubated at 35–37°C aerobically for 18–24 h. From each of the incubated plates, a culture suspension was prepared and the organisms were identified as described in the method. Printed results indicated a high probability match to a single species if a unique identification pattern was recognized. If a unique pattern was not recognized, the system suggested supplemental tests to distinguish between two or three closely related organisms, or indicated the result as an unidentified organism. As indicated in the VITEK 2 GP product information provided to end-users, slashline or low discrimination identifications were considered acceptable results for the VITEK 2 GP method that required supplemental tests to further resolve the organism identification. Results were classified as I, Identified; UD, Unidentified; and MI, Misidentified. The results of each isolate identification were recorded on the data reporting sheets provided and were sent along with the VITEK 2 printouts to the study director within 2 weeks of completion of the study. No additional testing was required for isolates not characterized as Gram-positive organisms by Gram stain procedures. AOAC Official Method 2012.02 Gram-Positive Bacteria Identification VITEK ® 2 Gram Positive (GP) Biochemical Identification Method First Action 2012 (Applicable to the identification of Gram-positive bacteria, including Listeria and Staphylococcus species.) See Tables 2012.02A and 2012.02B for results of the interlaboratory study supporting acceptance of the method. Claimed Gram-positive species validated in both the precollaborative and collaborative studies: Listeria grayi, Listeria innocua, Listeria ivanovii ssp. Ivanovii, Listeria ivanovii ssp. Londoniensis, Listeria monocytogenes, Listeria seeligeri, Listeria welshimeri, Staphylococcus hyicus, Staphylococcus intermedius, Staphylococcus aureus, Staphylococcus aureus, and Staphylococcus epidermidis .
A. Principle The VITEK2 system is an automated microbial identification system that utilizes the VITEK 2 Gram-positive (GP) identification card for the identification of most significant Gram-positive organisms. The VITEK 2 GP card is based on 43 biochemical tests measuring carbon source utilization, inhibition and resistance, and enzymatic activities. Identification results are available in approximately 8 h or less. B. Apparatus and Reagents ( a ) VITEK 2 system. ( b ) VITEK 2 GP test cards. ( c ) Vortex. ( d ) Incubators .—Set to 30°C and 35–37°C. ( e ) VITEK 2 DENSICHEK kit. ( f ) DENSICHEK calibrator . ( g ) VITEK 2 cassette . ( h ) Sterile saline .—Aqueous 0.45 to 0.50% NaCl, pH 4.5 to 7.0). ( i ) Disposable test tubes .—12 mm × 75 mm clear plastic (polystyrene). ( j ) Sterile sticks or swabs. ( k ) Brain Heart Infusion (BHI) slants. ( l ) Culture media .—Columbia agar with 5% sheep blood (CBA), Trypticase soy agar (TSA), or Trypticase soy agar with 5% sheep blood (TSAB) plates. C. General Instructions ( a ) The test cannot be performed without a pure culture. A pure culture may be obtained by streaking out the isolate on CBA, TSA, or TSAB plates. ( b ) Gram stain purified isolate prior to preparingVITEK 2 GP test card to verify presence of Gram-positive organism. ( c ) Caution : Dispose of all reagents and other contaminated materials by acceptable procedures for potentially biohazardous materials. All microbial cultures are potentially infectious and should be treated with universal precautions.
03/10/2019
Made with FlippingBook Online newsletter