Rapid Identification of Bacteria by Mass Spectrometric Analysis

Post date:2019.02.25

In future, MALDI-TOF MS;Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometer is expected to be mainly used for identification of bacteria because of its convenient and rapid characteristics. It has been already introduced into clinical laboratories in major hospitals and universities, and the application to veterinary medicine is also expected.
Mass spectrometric analysis means to weigh molecules such as protein, and determine the kind of protein and the amount included in an unknown sample by its ionization. MALDI-TOF MS samples are ionized by irradiation of laser to samples mixed with a matrix material, and the weight of molecules is determined by the required time for flight of ions for a certain distance in a vacuum. This technology is based on Matrix Assisted Laser Desorption/Ionization which is developed by Mr. Koichi Tanaka, a Nobel Prize Laureate in Chemistry 2002, which shows Japans contribution to this field.
In the application for identification of bacteria, protein derived from bacteria is characterized depending upon the species of bacteria. It is revolutionary that bacterial identification by MALDE-TOF MS can be finished within only 5 minutes by using patterns of molecular weight information of protein in various bacteria. However, the point is that this device is too expensive, and that molecular weight information of bacterial protein leans to medical bacteriology, therefore, most of bacteria derived from animals and environment cannot be identified. Staphylococcus pseudintermedius which causes canine pyoderma had not been identified except for by genetic testing, however, recently, became able to identify by MALDE-TOF MS. In the future, the application range except for in human medicine will be greatly expanded by collecting information of bacteria derived from animals and environment. Moreover, application studies by MALDI-TOF- MS are numerous, such as indirect evaluation of antimicrobial resistance through detecting degradation products of beta-lactam drug. It does not progress to the commercialization stage, however, so future application is expected.
Our university, Rakuno Gakuen, has introduced MALDI-TOF-MS for the purpose of analysis of protein through funding from the Ministry of Education, Culture, Sports, Science and Technology. Although this MALDI-TOF MS has become quite old recently, it is frequently used for the identification of various bacteria. This device has made educational studies efficient, however remembering the existing way of identification by examining the gram stain and biochemical properties, and checking Bergey’s Manual, it makes me worried from a bacteriological educational point. Times may change, but bacterial identification is the foundation in bacteriology, and it remains unchanged to be based on the bacterial shapes and biochemical properties. I debate between fundamental classical techniques and the efficient latest technology.