Identification of nontuberculous mycobacteria at species level by matrix assisted laser desorption/ionization-time of flight mass spectrometry

Nontuberculous mycobacteria (NTM) are the microorganisms that is transmitted from environmental sources and leads to chronic infections. Nowadays more than 190 mycobacteria species are identified. Most of them have not been shown as an agent of infection yet. Treatment protocols of NTM show difference according to species. It is needed that an easy to perform, cheap and fast method for identification at species level. Matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) used in recent years have this features. With this aim, 22 Mycobacterium abscessus, 4 Mycobacterium chelonae, 37 Mycobacterium fortuitum, 5 Mycobacterium gordonae, 9 Mycobacterium intracellulare, 4 Mycobacterium kansasii, 1 Mycobacterium lentiflavum, 3 Mycobacterium szulgai isolates that are grown by cultures of patient samples sent to Dokuz Eylül University Central Laboratory between 2013-2019 and identified at species level by nucleic acid hybridization method are studied with MALDI-TOF MS in the study. 83/85 (%97.6) isolates are identified at species level by MALDI-TOF MS. The results of two tests are accepted as concordant for 81/85 (%95.2) isolates. Identification of NTM carries great importance for both acquiring true epidemiologic data and provide suitable antimicrobial management. MALDI-TOF MS appears as a suitable method for species identification of NTM. It is detected that it has high concordance with a molecular method in our study. It is a method that is easy to use, cost effective and gives result about 90 minutes. All of that, it is considered that better results will be taken by doing some improvements in its library. Key words: Nontuberculous mycobacteria, identification at species level, mass spectrometry, MALDI-TOF MS