Current Status of Matrix-Assisted Laser Desorption/Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) in Clinical Diagnostic Microbiology

Abstract

Mass spectrometry (MS), a core technology for proteomics and metabolomics, is currently being developed for clinical applications. The identification of microorganisms in clinical samples using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) is a representative MS-based proteomics application that is relevant to daily clinical practice. This technology has the advantages of convenience, speed, and accuracy when compared with conventional biochemical methods. MALDI-TOF MS can shorten the time used for microbial identification by about 1 day in routine workflows. Sample preparation from microbial colonies has been improved, increasing the accuracy and speed of identification. MALDI-TOF MS is also used for testing blood, cerebrospinal fluid, and urine, because it can directly identify the microorganisms in these liquid samples without prior culture or subculture. Thus, MALDI-TOF MS has the potential to improve patient prognosis and decrease the length of hospitalization and is therefore currently considered an essential tool in clinical microbiology. Furthermore, MALDI-TOF MS is currently being combined with other technologies, such as flow cytometry, to expand the scope of clinical applications.

Keywords: bacterial identification; blood culture; clinical proteomics; matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry (MALDI-TOF MS), sample preparation.

Figure 1

Identification process using matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry (MALDI-TOF MS) (MALDI Biotyper). Colony scraping technique using a sterile toothpick. Thecolony adhering to the toothpick was directly transferred onto a MALDI target plate for spotting. Immediately, 1 µL of 70% formic acid and matrix were spotted onto the MALDI target plate, and bacterial ID was performed with MALDI-TOF MS analysis using a MALDI Biotyper.