MALDI-TOF Mass Spectrometry

Next Generation Bacterial Identification Is Now Available at WADDL


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WADDL has added a MALDI-TOF mass spectrometer to its arsenal of diagnostic tools! Thanks to this technology the bacteriology lab is reporting preliminary results the day after the specimen arrives at the laboratory. Once the microorganism is isolated it can be accurately identified within minutes for many of the bacteriology submissions rather than 2-7 days when using traditional testing methods.

MALDI-TOF stands for Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry, an instrument that allows our microbiologists to quickly identify bacteria and fungi based on the organism’s protein composition. The MALDI-TOF uses a unique “protein fingerprint” to identify organisms such as bacteria, fungi and mycobacterium. This means that WADDL is able to produce accurate and molecular-based results faster than ever before once a microorganism has been isolated in the lab. 

The MALDI-TOF will also play an important role in various research and pathogen discovery projects in the College of Veterinary Medicine and other departments at Washington State University. 

Frequently Asked Questions


How Does the MALDI-TOF work?

The MALDI Biotyper® identifies microorganisms using MALDI-TOF Mass Spectrometry to measure the unique molecular fingerprint of an organism. Specifically, the MALDI Biotyper measures highly abundant proteins that are found in all microorganisms. The characteristic weight of these proteins determines patterns that are used to accurately and reliably identify a particular microorganism. Patterns are matched in an extensive open database to determine the identity of the microorganism down to the species level.

How is this different from traditional testing?

WADDL’s clients will benefit from the MALDI-TOF every time that a specimen is submitted to the bacteriology section. Once a microorganism has been isolated, its identification can be performed the same day with increased accuracy and precision. 

Is MALDI-TOF better than traditional testing?

Yes, results are available sooner (24-48 hours versus 2-7 days with conventional technology) and with a higher degree of accuracy over traditional culture methods. Traditionally, the identification of bacteria and fungus is accomplished by phenotypic characteristics, together with their response to biochemical tests. Conventional methods can take days or even weeks and in many cases, biochemical testing cannot differentiate between species of microorganisms and therefore identification is accomplished only to the genus level. Frequently, laboratories resort to molecular techniques for correct identification, which include additional costs. With the use of the MALDI-TOF, after a microorganism is isolated in the laboratory, it can be accurately identified within minutes. 

Does MALDI-TOF have limitations?

Yes, the MALDI-TOF used at WADDL is used in conjunction with a Biotyper ®, which is a software program designed to store the genetic fingerprint of tens of thousands of microorganisms. The fingerprint of the tested microorganism is compared with the Biotyper library and if the microorganism is not in the included in the library the MALDI-TOF won’t be able to identify it. In addition, some microorganisms, such as fungus and Mycobacterium species, are slow growers and require an additional extraction method that will delay the identification. There are some bacterial species belonging to certain families or genera in which the protein profiles are very similar. In these cases, the software may have difficulty in differentiating between them. However, because additional profiles are added to the library as the technology is adopted, the misidentification of pathogens will decrease over time.    

Who may benefit from the MALDI-TOF technology?

Once a microorganism has been isolated, its identification can be performed the same day with increased accuracy and precision, allowing the veterinarian to make a quicker diagnosis and treatment plan.  Additionally, the microorganism can be identified down to the species level at no extra cost negating the need for additional PCR testing.   

Does this cost more than traditional testing?

No, the price is the same as traditional testing.

How do I indicate that I want MALDI-TOF testing performed?

Use the General Accession Form and check the "Bacteriology" box.  We are using the MALDI-TOF whenever possible.

What type of samples are needed for MALDI-TOF testing?

The procedure for collection of samples is the same as for traditional methods. An isolated microorganism is required to use the MALDI-TOF as a tool for pathogen identification. For identification of bacteria and fungus, the ideal samples are fluids or tissues, although swabs may be used if those are not available. For more information about the guidelines for sample collection, refer to the Bacteriology User Guide or call the laboratory at (509) 335-9696.

Can MALDI-TOF be used directly on samples?

There is a kit that allows the use of MALDI-TOF directly from blood without initial culture for patients who are clinically suspected to be septicemic. The sample should be collected in blood culture bottles and the laboratory must be contacted in advance.       

How are results reported?

WADDL has professional microbiologists who analyze the results obtained from the MALDI-TOF in each case.  Submitters receive a report with a comment that MALDI-TOF has been used for the identification of a microorganism.  Cases are reported following a clinical microbiology interpretation.  Reports can be received by mail, fax or online.

What type of research can the MALDI-TOF be used for?

Currently we are analyzing the use of the MALDI- TOF to develop new ways to identify bacteria by protein "fingerprint' versus nucleic acid or biochemical "fingerprint".  The fingerprint  allows us to identify patterns among groups of bacteria.  We also collaborate with WSU researchers in a wide range of various projects. Contact us if you are wondering if MALDI-TOF is an alternative for your research project.