Mass spectrometry based methods for the discrimination and typing of mycobacteria

Identification and typing of mycobacteria is very important for epidemiology, susceptibility testing and diagnostic purposes. This paper describes the development and validation of the alternative methods for species identification and typing of mycobacteria based on a matrix-assisted laser desorption/ionization time-of-flight mass-spectrometry (MALDI-ToF MS). Altogether there were 383 clinical isolates analyzed which include 348 strains of Mycobacterium tuberculosis complex (MTBC) (342 strains of M. tuberculosis and 6 strains of M. bovis) and 35 strains of nontuberculous mycobacteria (NTM) represented by 16 different species. Direct bacterial profiling (DBP) by means of MALDI-ToF MS was carried out. Cluster analysis of DBP mass spectra divided them into two large separate groups corresponding to MTBC and NTM, and also demonstrated the possibility of isolate identification at the species level. Spoligotyping protocol based on mass spectrometry was developed and validated, it matched completely to classical spoligotyping data. Our results suggest that MALDI-ToF MS has potential as a rapid and reproducible platform for the identification and typing of Mycobacterium species.