VITEK MS Collaborative Study Outline - eBook

VITEK MS Collaborative Study

June 2019

5.8.3.3 The calibration strain, E. coli ATCC 8739, is deposited on the calibration well positions, depending on the number of samples tested (1 calibrator per acquisition group of 16 spots). Follow the directions for Preparation of bacteria isolates (beginning in 5.8.3.4) to prepare the E. coli ATCC 8739 calibration strain. 5.8.3.4.1 Make sure not to pick up any agar with the colony as this will have a negative impact on the spectrum. 5.8.3.4.2 Some microorganisms, such as Streptococci , grow as very small colonies. In such cases, several similar colonies may be selected and deposited on one spot. 5.8.3.5 Apply the sample to the center of the spot. Smear a thin layer of the sample on the spot, then discard the used loop. 5.8.3.6 Take special care not to apply too much organism. The appropriate amount of organism on a spot is shown in the picture below. If insufficient colony material is deposited, use a new loop and introduce additional organism to the spot. 5.8.3.4 Using a 1 μl loop, pick up part of a suitable colony.

5.8.3.7 Open the microtube containing the VITEK MS-CHCA matrix. Add precisely 1.0 μl of matrix to the center of the spot. Discard the pipette tip. The matrix/microorganism suspension is then left to dry completely. 5.8.3.8 It is strongly recommended to deposit the matrix as indicated in the VITEK MS Prep Station workflow for bacteria: 2 by 2 in duplicate mode or 1 by 1 in single mode. Note: The VITEK MS-CHCA matrix contains a high concentration of organic solvents; it is recommended to close the tube after dispensing to avoid evaporation. 5.8.3.9 Proceed likewise for each additional sample. 5.8.3.10 After five minutes, check for crystal formation on the spots. Use of a magnifying lens may be helpful. An accurate measurement requires that the matrix crystals

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