MALDI-TOF MS For the Diagnosis of Infectious Diseases

By Kelley Luedke • April 13, 2015

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Matrix-assisted laser desorption ionization time of flight (MALDI TOF) mass spectrometry (MS) offers a safe, cost-effective, and adaptable system for rapid identification of bacteria and fungi. MALDI-TOF MS is being rapidly embraced by laboratories around the globe for routine bacterial and fungal identification in clinical microbiology laboratories.

A recent review in Clinical Chemistry, by Robin Patel, M.D., Chair of the Division of Clinical Microbiology at Mayo Clinic, discusses how MALDI-TOF MS provides rapid, accurate, and cost-effective identification of cultured bacteria and fungi in clinical microbiology. It is used for the identification of aerobic and anaerobic bacteria, mycobacteria, and fungi, as well as testing urine samples and positive blood culture bottles.

While there are several preparatory methods used for MALDI-TOF MS, direct colony processing is easiest, fastest, and least expensive. A colony is “picked” from a culture plate to a “spot” on a MALDI-TOF–MS target plate. The addition of a formic acid solution to the MALDI plate may be used to improve the quality of the generated mass spectrum, which may be particularly helpful for certain types of organisms, such as yeasts (Figure 1). After drying, the target plate is placed in the mass spectrometer's ionization chamber (Figure 2).

MALDI-TOF MS performs at least as well as, if not better than, automated biochemical identification for commonly encountered bacteria and yeast. It has also become the method of choice for identification of anaerobic bacteria, replacing 16S rRNA gene sequencing and gas–liquid chromatography. MALDI-TOF MS has also proved useful for identification of mycobacteria with a few limitations, such as the inability to differentiate members of the Mycobacterium tuberculosis complex. In addition to bacteria, MALDI-TOF MS can identify yeasts.

In summary, MALDI-TOF MS is automated, high throughput, and applicable to a broad range of common as well as esoteric bacteria and fungi, making it an incontrovertibly beneficial technology for the clinical microbiology laboratory.

Additional Resources:

1. Bacterial Identification by Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (Hot Topic) by Robin Patel, M.D., Chair of the Division of Clinical Microbiology at Mayo Clinic
2. Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for the Identification of Bacterial and Yeast Isolates (Communiqué) by Elitza Theel, Ph.D., Director of the Infectious Disease Serology Laboratory at Mayo Clinic
3. Anaerobic Bacteria (Hot Topic) by Jon Rosenblatt, M.D., Consultant in the Division of Clinical Microbiology at Mayo Clinic

Kelley Luedke

Kelley Luedke is a Marketing Channel Manager at Mayo Clinic Laboratories. She is the principle editor and writer of Insights and leads social media and direct marketing strategy. Kelley has worked at Mayo Clinic since 2013. Outside of work, you can find Kelley running, traveling, playing with her kitty, and exploring new foods.