Pathology Consultation on Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Microbiology

Objectives: Traditional microbial identification methods are based on morphology (both micro- and macroscopic) and biochemical tests that require long incubation periods and a good deal of technologist hands-on time. In addition, many of these methods have some degree of subjectivity. In comparison, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) identifies microorganisms from colonies grown on solid media within minutes using very few reagents. Methods: A case-based approach was used to review the strengths and weaknesses of MALDI-TOF MS in clinical microbiology laboratories. Results: MALDI-TOF MS has been proven to be an accurate and reliable method for organism identification including bacteria, yeast, molds, and mycobacteria. It is rapid, with results often 24 hours earlier than traditional methods, and inexpensive. There are no FDA-approved systems available currently. Susceptibility data are still reliant on conventional methods. There are genetically similar organisms that cannot be discriminated reliably with this method. Conclusions: MALDI-TOF MS is an exciting, innovative method for organism identification in the clinical microbiology laboratory.