BLT Stages

Abstract Bachelor Project 2017-2018: Verification of a few susceptibility tests in a microbiological laboratory (Microvida – Terneuzen)

Microvida has decided to do a verification of the susceptibility tests for the three locations of Microvida because there is a requirement to uphold the high quality of the laboratory. By using ATCC strains of the AST ST03 card and the AST P657 card from VITEK, it is determined if the mentioned cards meet the required acceptance criteria. Secondly, it is determined whether the new paper-disk tablets meet the acceptance criteria.
Next, it is important to determine whether two identical plates from different locations differ from one another, to decide which plate would yield the best results. The final check is to determine whether the paper-disk tablets can be kept after five weeks without the quality decreasing.

The methods used, are MIC and Agar diffusion. The VITEK is counted under the MIC. A suspension consisting out of 0,9% saline and bacteria to a McFarland of 0.5 is made for these verifications. Then a dilution is performed from the inoculum that just was made. This tube is used to do a VITEK AST determination.

The disk diffusion and the ESBL belong to the Agar diffusion. For the ESBL the PCR was used as a reference method. The Agar diffusion is executed as follows : first an inoculum is made with 0,9% saline and bacteria at a McFarland of 0,5. This is spread on a suitable plate for susceptibility testing. Next, the analyst applies the disks. Subsequently the plates go into the appropriate stove and the following day the results can be read. There it can be decided if there is a 5 mm difference or more, then it is a positive ESBL. For the disk diffusion, we measure if everything is within the ranges. 

For the VITEK the AST ST03 card and the AST P657 card from the VITEK meet the acceptance criteria.
The new paper-disk tablets meet the acceptance criteria. 100 % of the paper-disk tablets meet the ranges for the Disk diffusion and ESBL. The two tested plates are equal to each other with no major differences.
The paper-disk tablets are still valuable after five weeks with no decrease in quality.