Current developments to use linear MALDI‐TOF spectra for the identification and typing of bacteria and the characterization of other cells/organisms related to infectious diseases

Abstract

Within the past few years identification of bacteria by MALDI-TOF MS has become a standard technique in bacteriological laboratories for good reasons. MALDI-TOF MS identification is rapid, robust, automatable, and the per-sample costs are low. Yet, the spectra are very informative and the reliable identification of bacterial species is usually possible. Recently, new MS-based approaches for the identification of bacteria are emerging that are based on the detailed analysis of the bacterial proteome by high-resolution MS. These "proteotyping" approaches are highly discriminative and outperform MALDI-TOF MS-based identification in terms of specificity, but require a laborious proteomic workflow and far more expertise and sophisticated instrumentation than identification on basis of MALDI-TOF MS spectra, which can be obtained with relative simple and uncostly linear MALDI-TOF mass spectrometers. Thus MALDI-TOF MS identification of bacteria remains an attractive option for routine diagnostics. Additionally, MALDI-TOF MS identification protocols have been extended and improved in many respects making linear MALDI-TOF MS a versatile tool that can be useful beyond the identification of a bacterial species, e.g. for the characterization of leucocytes and arthropod vectors of infectious diseases. This review focuses on such improvements and extensions of the typical MALDI-TOF MS workflow in the field of infectious diseases.

Improved Discrimination of Bacillus anthracis from Closely Related Species in the Bacillus cereus Sensu Lato Group Based on Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

“…However, MALDI-TOF MS is used as a fast, first-line tool for identification and may orchestrate subsequent diagnostic methods. The success of identification of the bacteria by means of mass spectrometry relies on three different aspects: sample preparation and protein extraction, mass spectrometric analysis, and subsequent statistical evaluation for identification (26). For diagnostic laboratories, results obtained with any database, whether commercial or generated in-house, have significant consequences for the appropriate treatment of the patient.…”

“…However, to further improve identification and discrimination of closely related species, extended statistical evaluations are needed. Implementation of multivariate statistics using additional software, such as ClinProTools (Bruker) and Matlab (The Mathworks Inc.) in combination with different packages for the statistical programming language R could be used to reveal species-specific peaks which are normally hidden in complicated mass spectra (26). The use of decision trees (26) could allow automated marker-based identification and could be added to the statistical workflow.…”

MALDI-TOF MS Profiling-Advances in Species Identification of Pests, Parasites, and Vectors

“…Furthermore, in certain cases such as Leishmania subtyping, which is crucial for treatment, identification generally requires several weeks for performing complex and expensive analyses (Roelfsema et al, 2011). In recent years, proteome based linear matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS profiling or MALDI MS typing), which is a well-established technique for microbial species identification, has also been successfully applied to a variety of parasites and their vectors (Seng et al, 2009; Bizzini and Greub, 2010; Patel, 2013; Nomura, 2015; Karger, 2016; Singhal et al, 2016; Yssouf et al, 2016). The popularity of the method is due to its rapidness, easy to use, high throughput analysis, accuracy, reliability equal to that of the molecular methods of species identification and cost-effectiveness despite the initial cost of the machine (Dhiman et al, 2011; Neville et al, 2011; Tran et al, 2015; Ge et al, 2016).…”

“…The database extension has been utilized to create additional reference spectra to enhance the identification confidence and to include reference spectra of the missing species, including higher organisms (Bohme et al, 2012; Murugaiyan et al, 2012, 2014; Hoppenheit et al, 2013). Several reviews have been dedicated to the recent developments of MALDI MS typing of plant nematodes and organisms related to parasitology (Ahmad and Babalola, 2014; Karger, 2016; Singhal et al, 2016; Yssouf et al, 2016). Therefore, the focus of this review is on the various approaches reported for MALDI MS typing based species identification of pests, parasites, and their vectors ranging from laboratory isolates to that of field samples.…”

Quantification analysis of protein and mycelium contents upon inhibition of melanin for Aspergillus niger: a study of matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS)

“…24 MALDI-MS has a prominent role in the eld of biomedical science and medicine. 25 Mass spectra provide a ngerprint of the investigated microorganism; such as bacteria 20,[26][27][28][29][30] and fungal species. 31,32 The identication of fungal species is important for clinical medicine and food production.…”