Comparison of the New VITEK MS PRIME System with the Matrix-Assisted Laser Desorption Ionization Biotyper Microflex LT for the Identification of Microorganisms.

BACKGROUND

Matrix-assisted laser desorption ionization (MALDI) is the cornerstone of bacterial identification. The performance of a new MALDI time-of-flight mass spectrometry VITEK MS PRIME (VMS-P) system was compared with that of the MALDI Biotyper Microflex LT (MBT) system, which is routinely used in our laboratory.

METHODS

Sixteen bacterial and yeast reference strains cultured in 20 different media were analyzed over 10 consecutive rounds using both systems. Bacterial and yeast isolates from the routine workflow were processed using both systems. Microcolonies were identified after a 4-hour agar subculture from positive blood culture bottles, without extraction.

RESULTS

To determine the repeatability based on the reference strains, 1,190 spots were processed using each system. Correct identification was achieved for 94.0% (MBT) and 98.4% (VMS-P; <0.01) of spots. Among these, 83.0% (MBT) and 100.0% (VMS-P) were identified with a high degree of confidence. For 1,214 spots from routine isolates, species identification was achieved for 90.0% (MBT) and 91.4% (VMS-P; =0.26) of spots. For 69.8% (MBT) and 87.4% (VMS-P) of the spots, identification was achieved with a high degree-of-confidence score. When identification was performed using both systems, the agreement between them was 97.9%. The identification of microcolonies from positive blood culture bottles was achieved for 55.5% (MBT) and 70.2% (VMS-P; =0.01) of spots.

CONCLUSIONS

The MBT and VMS-P systems perform similarly in routine daily practice. The new VMS-P system shows high repeatability, better confidence scores for identification, and promising ability to identify microcolonies.