MALDI-TOF Advantages and Disadvantages

MALDI-TOF Advantages and Disadvantages Abstract Rapid diagnosis of microbial pathogens or infections in clinical laboratories is decisive to guarantee accurate therapy and efficient patient care. Although the conventional method, which is mostly based on biochemical testings and long incubation procedures, are precise and sensitive; they are rather slow. Until recently, matrix-assisted laser desorption-ionization-time of flight (MALDI-TOF) has emerged as a powerful technique for identification of microorganisms in clinical microbiology. MADLI-TOF has the advantage of identifying bacterial or fungal species directly on the culture plates as fast as 10 to 15 minutes in a few simple steps. The principle behind MALDI-TOF is based on mass spectrometry and soft ionization technique. Depending on the time of flight of each pathogen, the characteristic spectrum will be analyzed and displayed via the inbuilt software. This review describes the advantages and limitations of MALDI-TOF. It also compares the identification efficacy of bacteria between MALDI-TOF and the culture methods. There are several comparative studies between the conventional techniques and the MALDI-TOF systems in terms of reliability and accuracy of their methods. Keywords: MALDI-TOF, diagnostic microbiology, spectrometry Introduction Microbiological identification of pathogenic bacteria and fungi has used to be performed by conventional methods which involved long process of culturing and biochemical/phenotypic testings. Although cultures are powerful methods in retrieving pathogens, multiplying a single viable pathogen in an appropriate medium logarithmically, it is time consuming and the phenotypic tests could delay over 24 to 48 hours. In the circumstances, such as bacteremia, which requires a rapid diagnosis and treatment, delay in adequate management could cause mortality to rise by 10 to 20% as shown by Kumar et al.. Length of hospital stay and the price of admission equally decrease with early identification of the etiology of sepsis. New diagnostic methods have been developed, and they do not depend on bacterial or fungal growth and are effective even when the pathogens are not viable. The methods employing nucleic acids are already in clinical use; however, although faster than cultures, they demand tech nical time and at least 6 to 8 hours of work by a dedicated professional. A major advance is the use of proteomic studies for rapid diagnosis as fast as 5 to 15 minutes of etiology of infections, and it is represented by MALDI-TOF. THE IMPORTANCE OF MALDI-TOF Mass Spectrometry Mass spectrometry is an analytical technique that measures ionized chemical compounds based on their mass to charge (m/z) ratio (). By combining the technique of ionization and biomolecular detection from mass spectrometry (), matrix assisted laser desorption ionization-time of flight (MALDI-TOF) was developed and is widely used in microbiological diagnosis (). There are three main units that compose the MALDI-TOF spectrometer: ion source, mass analyzer, and detection device (). The purpose of the ion source is to ionize molecules thus transferring them into the subsequent gas phase (). The mass analyzer unit aids in ion separation based on mass to charge ratio (). Lastly, detection device is there for monetization of separated ions (). Principles and methodologies In order for MALDI-TOF to begin processing the biological material (ex: a colony or a blood culture concentrate), sample is placed on a plate containing polymeric matrix (). Next, irradiation occurs through the medium of a laser (). During the process, laser would also vaporize and ionize molecules within the sample (). Afterwards, aspiration of those molecules into the vacuum tube will transport them to the detection device (). Depending on which bacterial or fungal specie is being examine, the time of flight will also be different (). Lastly, the computerized database of MALDI-TOF will generate a chart with different peaks-providing results and interpretations all very quickly (). Advantages A major advantage of MALDI-TOF is its rapid turnaround time (