The Next Generation Technology for Microbial Identification: MALDI-TOF

Accugenix has adopted this mass spectrometry (MS)-based method that focuses on the ribosomal proteins as the first practical proteotypic system to utilize MALDI-TOF technology for bacterial identification. The result is a highly accurate identification based on molecules that are translated from DNA but are not subject to the expression variability seen in phenotypic methods. These ribosomal protein molecules are constitutively expressed and structural, so they are consistently present in the cell in very high numbers.

Accugenix has optimized MALDI-TOF for use in bacterial identification with the AccuPRO-ID® service. When an initial ID cannot be made by the MALDI-TOF technology, the AccuPRO-ID® service offering automatically transfers your sample to our 16S rDNA sequencing technology with its substantial database, at no additional cost, providing clients with highly accurate results.

Simplicity and Accuracy

  • MALDI-TOF is a mass spectrometry technology utilizing a solid phase ionization process.
  • A small amount of bacterial sample is suspended in a solution containing a matrix (cell lysing, UV-absorbing compound) and placed onto a 96-well target plate for analysis.
  • Samples can be submitted on plates or as ethanol preparations for AccuPRO-ID®.
  • The mixture is allowed to dry on a plate prior to laser-irradiation.
  • The dried sample is placed in the vacuum source chamber of the TOF MS machine and irradiated with a pulsed laser beam.
  • The soft ionization MALDI-TOF process utilizes the matrix to absorb laser energy while protecting the proteins and transferring ions to the large biomolecules (the proteins remain intact).
  • The proteins are released from the matrix and enter the gaseous state as charged molecules.
  • Ions accelerated by high electric fields are then separated based on the time it takes them to travel a specified distance in the flight tube – Time of Flight (TOF).
  • Ions with the same charge are emitted at the same time from the source with the same kinetic energy.
  • The lower the mass of the ion, the higher its velocity, and the faster it will reach the detector.
  • The detector records each ion that strikes, and because ions have mass-dependent velocities, their mass is determined by their time of flight.
  • The sample’s protein spectrum or fingerprint that emerges from this process for each sample is recorded as an average of hundreds of laser excitation events and is based primarily on the ribosomal proteins.
  • The spectra are then compared to our validated database of spectra from known microbes for identification.
  • The Accugenix AccuPRO-ID® Proteotypic Solution provides a cGMP compliant identification report. The report incorporates an easily interpreted identification and confidence level. Our interpretation is based on the current taxonomy in IJSEM (International Journal of Systematic and Evolutionary Microbiology).

 

Accugenix continually strives to improve the protein-spectra database of the protein-based identification system to include organisms that are relevant to the industries we serve. Thus, we are constantly adding new spectra from new organisms to the library to improve the frequency of identification. At Accugenix, our goal is to provide you with a species level identification and we have the expertise required to advance the MALDI-TOF database to provide you a higher level of accuracy.

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