Identification of mycobacteria species through mass spectrometry (MALDI-TOF)

Abstract

Mycobacterial diseases are very important both clinically and epidemiologically. Mycobacterium tuberculosis complex (MTBc) infections confer higher morbidity and mortality rate than non-tuberculous mycobacteria (NTM) infections. Traditional species identification techniques are based on phenotypic characteristics which take a long time by laborious processes and in occasions are no conclusive. Currently, most used techniques are based on molecular methods, which are accurate but are expensive and complex. Matrix Assisted Laser Desorption/Ionization Time-of-Flight mass spectrometry (MALDI-TOF MS) is a simple, cheap and fast identification method based on comparing protein spectra with a reference database. To assess the performance of MALDI-TOF MS in the identification of MTBc and NTM, compared with molecular methods. For that purpose, 28 isolates of 9 different species were analyzed through MALDI-TOF MS. 78.5% (22/28) of isolates were correctly identified, 100% (9/9) of rapidly growers NTM, 60% (9/15) of slow growing NTM and 100% (4/4) of MTBc. Every unidentified isolate (6/6) corresponded to M. avium/intracellulare complex. MALDI-TOF MS is fast, simple and cheaper than molecular methods and also has adequate accuracy.