VITEK MS Collaborative Study Outline - eBook

1 

bacteria and yeast. See Table 1 for complete list.

( b ) Summary of Validated Performance Claims .– The VITEK MS was validated for the detection of  2  Gram‐negative and Gram‐positive, aerobic and anaerobic bacteria, and yeast. The method  3  correctly identified 95.5% of the microorganisms correctly: 94.4% Gram negative organisms,  4  96.1% Gram positive organisms and 97.5% yeast organisms using the combined internal and  5  independent study data. 

6  7  8 

Definitions  

( a ) Percent agreement.— The percentage of time the organism was correctly identified by the VITEK  9  MS method. 

10  11 

Principle of the Method  12  The VITEK MS is a mass spectrometer based on MALDI‐TOF (MALDI: Matrix‐assisted laser  13  desorption/ionization; TOF: Time‐of‐Flight) technology. A portion of a colony from an agar plate is  14  applied to a spot on a VITEK MS‐ DS target slide. A matrix solution is applied to the spot on the VITEK  15  MS‐DS target slide. The VITEK MS‐DS target slide is dried and then loaded into the VITEK MS. The sample  16  is submitted to multiple laser shots inside the VITEK MS mass spectrometer. The matrix absorbs the  17  laser light and vaporizes, along with the sample, in the process gaining an electrical charge (ionization).  18  Electric fields then guide the ions into the vacuum tube which separates them according to 'weight'  19  (mass, the smaller molecules flying faster than the larger ones), and their time of flight, and displays the  20  results as a series of lines or peaks (spectrum) which correspond to different fragments that have  21  broken away from the original molecules in the sample. By analyzing the pattern of fragments it is  22  possible to deduce the structure of the molecules. The sample spectra are compared to a database of  23  spectra developed from a number of bacterial species. The sample spectra are interpreted to provide  24  organism identification results associated with a confidence level. 

25  26  27  28  29  30  31  32  33  34  35  36  37  38

Materials and Methods 

Test Kit Information  

( a )   Kit Name .—VITEK ® MS ( b )  Catalog Number .—411071 

( c )    Ordering Information

USA – (800) 634 7656, prompt 1   Europe –  +33 4 78 87 77 51  Asia/Pacific – +33 4 78 87 77 51 

Additional supplies and reagents required but not provided 

(a) VITEK MS‐CHCA matrix (Ref. 411071)  (b) VITEK MS‐FA (formic acid, Ref. 411072)  

Page 2 of 58