Mass spectrometry-based microbiological testing for blood stream infection

Abstract

Background: The most successful application of mass spectrometry (MS) in laboratory medicine is identification (ID) of microorganisms using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in blood stream infection. We describe MALDI-TOF MS-based bacterial ID with particular emphasis on the methods so far developed to directly identify microorganisms from positive blood culture bottles with MALDI-TOF MS including our own protocols. We touch upon the increasing roles of Liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) as well. Main body: Because blood culture bottles contain a variety of nonbacterial proteins that may interfere with analysis and interpretation, appropriate pretreatments are prerequisites for successful ID. Pretreatments include purification of bacterial pellets and short-term subcultures to form microcolonies prior to MALDI-TOF MS analysis. Three commercial protocols are currently available: the Sepsityper ® kit (Bruker Daltonics), the Vitek MS blood culture kit (bioMerieux, Inc.), and the rapid BACpro ® II kit (Nittobo Medical Co., Tokyo). Because these commercially available kits are costly and bacterial ID rates using these kits are not satisfactory, particularly for Gram-positive bacteria, various home-brew protocols have been developed: 1. Stepwise differential sedimentation of blood cells and microorganisms, 2. Combination of centrifugation and lysis procedures, 3. Lysis-vacuum filtration, and 4. Centrifugation and membrane filtration technique (CMFT). We prospectively evaluated the performance of this CMFT protocol compared with that of Sepsityper ® using 170 monomicrobial positive blood cultures. Although preliminary, the performance of the CMFT was significantly better than that of Sepsityper ® , particularly for Gram-positive isolates. MALDI-TOF MS-based testing of polymicrobial blood specimens, however, is still challenging. Also, its contribution to assessment of susceptibility and resistance to antibiotics is still limited. For this purpose, liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) should be more useful because this approach can identify as many as several thousand peptide sequences. Conclusion: MALDI-TOF MS is now an essential tool for rapid bacterial ID of pathogens that cause blood stream infection. For the purpose of assessment of susceptibility and resistance to antibiotics of the pathogens, the roles of liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) will increase in the future.

Current Status of Matrix-Assisted Laser Desorption/Ionization–Time-of-Flight Mass Spectrometry (MALDI-TOF MS) in Clinical Diagnostic Microbiology

“…Furthermore, regardless of how analytical methods including MS progress, these methods must be evaluated and implemented by experienced clinical microbiologists parallel to the use of conventional techniques. In view of this, the development of excellent human resources is essential along with improvements in the application of novel clinical laboratory methods [ 6 , 90 ].…”

“…MS has shown much progress within two main categories: searching for novel diagnostic biomarkers via comprehensive proteome/metabolome analyses [ 2 , 3 , 4 ] and clinical microbiology testing [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. The present review focuses on clinical microbiology testing.…”

“…Matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry (MALDI-TOF MS) is one of the most widely used MS methods applied to the identification of microorganisms in clinical samples [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. This new application has proven useful in the diagnosis and treatment of infectious diseases that require a swift response.…”

Application of MALDI-TOF MS Profiling Coupled With Functionalized Magnetic Enrichment for Rapid Identification of Pathogens in a Patient With Open Fracture

“…In recent years, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been introduced into clinical microbiology laboratories. Due to the specificity, speed of analysis, and low cost of consumables, MALDI-TOF MS has been widely acclaimed for clinical bacterial identification (Welker et al, 2019;Feng et al, 2020;Nomura et al, 2020;Papagiannopoulou et al, 2020). MALDI-TOF MS identification is mainly based on the MS fingerprint pattern of bacterial ribosomal proteins in the m/z range of 2-20 kDa, which can be compared to the MS database to identify the bacterial genus and species (Singhal et al, 2015).…”

Novel electronic biosensor for automated inoculum preparation to accelerate antimicrobial susceptibility testing

“…The relatively recent introduction of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) technology into the clinical microbiology laboratory has revolutionized the identification of microorganisms and is significantly faster than traditional biochemical methods. Several laboratories have reported utilizing MALDI-TOF with direct from PBC protocols which can generate an ID result within one to two hours of a blood culture bottle flagging positive 9 , 23 , 24 . Other currently available rapid ID platforms include VERIGENE (Luminex, Austin, TX), BioFire (BioMérieux) and ePlex System (GenMark Dx).…”