Abstract
Problem with mass spectrometers is the difficulty in identifying some genera of acid-fast bacteria (AFB). Due to the peculiarities of the colony architectonics (the formation of dry colonies with a complex structure) and the structure of the cell wall, the probability of obtaining a sufficient amount of ribosomal proteins is significantly reduced. This problem is partially solved using an extended method of direct application and extraction with formic acid, which can significantly improve the quality of the identification. The study analyzed strains of microorganisms obtained during the examination of patients with suspected tuberculosis. In total, 287 strains of nontuberculous mycobacteria (NTM) were obtained. In addition, 63 strains of the most common bacteria from the AFB group were analyzed. Matrix-assisted laser desorption/ionization (MALDI) was used. Three main methods of sample preparation of microorganisms according to the manufacturer's recommendations for use with the MALDI-time-of-flight (ToF) mass spectrometry method were used in the work: Direct coating method, extended direct coating method, and formic acid extraction method. When evaluating the influence of the cultivation medium on the result of NTM identification by MALDI-ToF mass spectrometry, statistically significant results of the influence of the medium on the result of NTM identification were revealed for all compared parameters. Optimization of sample preparation protocols and assessment of the impact on the identification of new methods of cultivating microorganisms can significantly improve the quality of the identification of both clinically significant microorganisms from the AFB group and saprophytic microflora, the clinical significance of which has not been proven at the moment.
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