It’s in the library!

The principle behind identification of microorganisms with MALDI Biotyper is the comparison of the mass spectrum of an unknown organism with a library of reference mass spectra - the MSPs (main spectra) of the MALDI Biotyper. It’s obvious that the specificity of species identification depends on the species/strain coverage of the reference spectrum library. Bruker therefore invested substantial resources to collecting as many strains as possible to build up the most comprehensive library. The major contributors are the 26 laboratories of the International Mycobacterium Consortium, providing well characterized clinical strains from which more than 470 reference entries have been derived.

In the course of reference spectra creation for the MBT Mycobacteria IVD library, mycobacteria were cultivated on liquid and solid media and resulting spectra compared. To prevent redundant reference entries (MSPs), in general, spectra from only one culture medium (liquid or solid) are included in the library when no differences were observed. For mycobacteria species where only one or two strains were available, references from both types of media are included. Hence the library can conveniently be applied for samples independent from growth on liquid or solid medium.

Mycobacteria are robust microorganisms. Although the MycoEX preparation protocol is optimized for Mycobacterium spp., some samples may result in mass spectra of intermediate quality. The MBT Mycobacteria software module integrates the mycobacteria workflow for samples that have been prepared using the MycoEX method into MBT Compass software, allowing processing of mass spectra with potentially lower quality than those obtained from most other bacteria.

Installing the module allows you to choose the new sample type mycobacteria. Samples flagged as mycobacteria will undergo an optimized acquisition method and spectra are automatically compared to the Mycobacteria Library. Standard samples can also be measured on the same MALDI target plate – no user intervention is required during measurement and processing. Adapted confidence thresholds for Mycobacteria identification assure high identification sensitivity without loss of specificity.