VITEK MS Collaborative Study Outline - eBook

VITEK MS Collaborative Study

June 2019

1.0 Introduction The goal of this collaborative study is to estimate the reproducibility of the bioMérieux VITEK ® MS Microbial Identification system for the identification and confirmation of bacteria (Gram-positive and Gram-negative, aerobic and anaerobic) and fungal isolates. Twelve (12) Gram-positive, 12 Gram- negative and 12 fungal isolates will be shipped to each collaborator for analysis on the VITEK MS Microbial Identification system. The total number of correct identification for each specific organism, for each group of organisms and for all organisms will be determined. 1.1 Description of the VITEK ® MS Microbial Identification workflow. The VITEK MS System is a bacterial and fungal identification system which uses MALDI-TOF (MALDI: Matrix-assisted laser desorption/ionization; TOF: Time-of-Flight) mass spectrometry technology. A portion of a colony from an agar plate is applied to a spot on a VITEK MS-DS target slide. A matrix solution is applied to the spot on the VITEK MS-DS target slide. The VITEK MS-DS target slide is dried and then loaded into the VITEK MS. The sample is submitted to multiple laser shots inside the VITEK MS mass spectrometer. The matrix absorbs the laser light and vaporizes, along with the sample, in the process gaining an electrical charge (ionization). Electric fields then guide the ions into the vacuum tube which separates them according to 'weight' (mass, the smaller molecules flying faster than the larger ones), and their time of flight, and displays the results as a series of lines or peaks (spectrum) which correspond to different fragments that have broken away from the original molecules in the sample. By analyzing the pattern of fragments, it is possible to deduce the structure of the molecules. The sample spectra are compared to a database of spectra developed from a number of bacterial species. The sample spectra are interpreted to provide organism identification results associated with a confidence level. 1.2 Summary of the Precollaborative Studies The VITEK MS was validated according to AOAC guidelines for Performance Tested Methods SM and Official Methods of Analysis SM precollaborative studies for the identification and confirmation of microorganisms. In the combined internal and independent laboratory studies, 359 different claimed organisms (representing 208 Gram-negative, 123 Gram-positive and 28 fungal isolates) were evaluated by the VITEK MS method. All test strains were cultured on appropriate agar medium and growth conditions before analyzing on the VITEK MS instrument. Overall percent correct identification in the combined Internal and Independent studies (6122/6413 VITEK MS results from the 359 different organisms) was 95.5%. For each specific group of microorganisms tested, the percent correct identification was 94.4% for Gram-negative organisms, 96.1% for Gram-positive organisms and 97.5% for fungal organisms. The VITEK MS reagents were stable over 12 month time studies and provided reproducible results when compared between lots. Assay ruggedness was demonstrated for three critical parameters, including the use of 1-µL loops from two different suppliers, the age of the culture on an agar

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