Pushing the Limits of MALDI-TOF Mass Spectrometry: Beyond Fungal Species Identification
16 Oct 2015-Journal of Fungi (Multidisciplinary Digital Publishing Institute)-Vol. 1, Iss: 3, pp 367-383
TL;DR: In this article, a review of the use of MALDI-TOF in the clinical mycology laboratory is presented, focusing on present and future applications of this versatile analytical tool in the field of bioinformatics.
Abstract: Matrix assisted laser desorption ionization time of flight (MALDI-TOF) is a powerful analytical tool that has revolutionized microbial identification. Routinely used for bacterial identification, MALDI-TOF has recently been applied to both yeast and filamentous fungi, confirming its pivotal role in the rapid and reliable diagnosis of infections. Subspecies-level identification holds an important role in epidemiological investigations aimed at tracing virulent or drug resistant clones. This review focuses on present and future applications of this versatile tool in the clinical mycology laboratory.
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TL;DR: Current and future molecular technologies used for fungal identification, and some of the problems associated with development and implementation of these technologies in today’s clinical microbiology laboratories are discussed.
Abstract: Diagnosing fungal infections poses a number of unique problems, including a decline in expertise needed for identifying fungi, and a reduced number of instruments and assays specific for fungal identification compared to that of bacteria and viruses.These problems are exacerbated by the fact that patients with fungal infections are often immunosuppressed, which predisposes to infections from both commonly and rarely seen fungi. In this review, we discuss current and future molecular technologies used for fungal identification, and some of the problems associated with development and implementation of these technologies in today's clinical microbiology laboratories.
90 citations
TL;DR: This minireview aims to provide an overview of currently available online databases for the taxonomy and identification of human and animal-pathogenic fungi and calls for the establishment of a cloud-based dynamic data network platform.
Abstract: The increase in public online databases dedicated to fungal identification is noteworthy. This can be attributed to improved access to molecular approaches to characterize fungi, as well as to delineate species within specific fungal groups in the last 2 decades, leading to an ever-increasing complexity of taxonomic assortments and nomenclatural reassignments. Thus, well-curated fungal databases with substantial accurate sequence data play a pivotal role for further research and diagnostics in the field of mycology. This minireview aims to provide an overview of currently available online databases for the taxonomy and identification of human and animal-pathogenic fungi and calls for the establishment of a cloud-based dynamic data network platform.
39 citations
Cites background from "Pushing the Limits of MALDI-TOF Mas..."
...complex and requires access to validated purpose-built databases of reference spectra (6, 7)....
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TL;DR: New molecular-based approaches for detecting triazole resistance to Aspergillus, real-time polymerase chain reaction (PCR) to detect mutations to the Cyp51A protein, have been developed which are able to detect mostTriazole-resistant A. fumigatus strains in patients with invasive aspergillosis.
Abstract: The incidence of invasive aspergillosis has increased substantially over the past few decades, accompanied by a change in susceptibility patterns of Aspergillus fumigatus with increasing resistance observed against triazole antifungals, including voriconazole and isavuconazole, the most commonly used antifungal agents for the disease. Culture-based methods for determining triazole resistance are still the gold standard but are time consuming and lack sensitivity. We sought to provide an update on non-culture-based methods for detecting resistance patterns to Aspergillus. New molecular-based approaches for detecting triazole resistance to Aspergillus, real-time polymerase chain reaction (PCR) to detect mutations to the Cyp51A protein, have been developed which are able to detect most triazole-resistant A. fumigatus strains in patients with invasive aspergillosis. Over the last few years, a number of non-culture-based methods for molecular detection of Aspergillus triazole resistance have been developed that may overcome some of the limitations of culture. These molecular methods are therefore of high epidemiological and clinical relevance, mainly in immunocompromised patients with hematological malignancies, where culture has particularly limited sensitivity. These assays are now able to detect most triazole-resistant Aspergillus fumigatus strains. Given that resistance rates vary, clinical utility for these assays still depends on regional resistance patterns.
19 citations
TL;DR: Fast, accurate and inexpensive molecular mass determination and the possibility of automation make MALDI-TOF-MS a real alternative to conventional morphological and molecular methods for AMF identification.
Abstract: Arbuscular mycorrhizal fungi (AMF, Glomeromycota) are mutualistic symbionts associated with majority of land plants. These fungi play an important role in plant growth, but their taxonomic identification remains a challenge for academic research, culture collections and inoculum producers who need to certify their products. Identification of these fungi was traditionally performed based on their spore morphology. DNA sequence data have successfully been used to study the evolutionary relationships of AMF, develop molecular identification tools and assess their diversity in the environment. However, these methods require considerable expertise and are not well-adapted for “routine” quality control of culture collections and inoculum production. Here, we show that Matrix-Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry proteomic-based biotyping is a highly efficient approach for AMF identification. Nineteen isolates belonging to fourteen species, seven genera and five families were clearly differentiated by MALDI biotyping at the species level, and intraspecific differentiation was achieved for the majority. AMF identification by MALDI biotyping could be highly useful, not only for research but also in agricultural and environmental applications. Fast, accurate and inexpensive molecular mass determination and the possibility of automation make MALDI-TOF-MS a real alternative to conventional morphological and molecular methods for AMF identification.
19 citations
TL;DR: The role of MALDI-TOF MS as a tool for species identification; in particular with respect to DNA-based identification methods is discussed, and the value of custom-made reference spectra for MalDI biotyping is highlighted.
Abstract: Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS; MALDI biotyping) has become a standard tool for the accurate, rapid, and economical identification of pathogens in the clinical diagnostics laboratory. The method is continuously being improved, and new applications for distinguishing strains, identifying metabolites or functional characteristics (e.g., antibiotic resistance), and detecting microbes directly in patient samples have been developed. Adopting these methods in other disciplines than clinical diagnostics, for example, in agriculture, food safety and quality testing, or ecology, will open up new opportunities for diagnostics and research. This review focuses on MALDI-TOF MS approaches for the identification of yeasts and filamentous fungi. In contrast to bacterial diagnostics, MALDI biotyping of fungi is more challenging and less established. We thus start by discussing the role of MALDI-TOF MS as a tool for species identification; in particular with respect to DNA-based identification methods. The review then highlights the value of custom-made reference spectra for MALDI biotyping and points out recent advancements of MALDI-TOF MS, mainly from the field of clinical diagnostics that may be adopted and used for fungal diagnostic challenges. The overview ends with a summary of MALDI-TOF MS studies of yeasts and filamentous fungi of agricultural relevance.
16 citations
Cites background from "Pushing the Limits of MALDI-TOF Mas..."
...Consequently, the majority of MALDI-TOF analyses of fungi so far have dealt with clinical isolates [33]....
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References
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TL;DR: It is shown that MALDI-TOF MS is a practicable alternative to conventional mycology or DNA-based methods for Cryptococcus identification at the species and subspecies levels by using an in-house database of 25 reference cryptococcal spectra.
Abstract: We evaluated the usefulness of matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) for Cryptococcus identification at the species and subspecies levels by using an in-house database of 25 reference cryptococcal spectra. Eighty-one out of the 82 Cryptococcus isolates (72 Cryptococcus neoformans and 10 Cryptococcus gattii) tested were correctly identified with respect to their molecular type designations. We showed that MALDI-TOF MS is a practicable alternative to conventional mycology or DNA-based methods.
90 citations
TL;DR: The results suggest that MALDI-TOF MS could be a useful tool for routine and fast identification of dermatophytes and Neoscytalidium spp.
Abstract: Dermatophytes are keratinolytic fungi responsible for a wide variety of diseases of glabrous skin, nails, and hair. Their identification, currently based on morphological criteria, is hindered by intraspecies morphological variability and the atypical morphology of some clinical isolates. The aim of this study was to evaluate matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) as a routine tool for identifying dermatophyte and Neoscytalidium species, both of which cause dermatomycoses. We first developed a spectral database of 12 different species of common and unusual dermatophytes and two molds responsible for dermatomycoses (Neoscytalidium dimidiatum and N. dimidiatum var. hyalinum). We then prospectively tested the performance of the database on 381 clinical dermatophyte and Neoscytalidium isolates. Correct identification of the species was obtained for 331/360 dermatophytes (91.9%) and 18/21 Neoscytalidium isolates (85.7%). The results of MALDI-TOF MS and standard identification disagreed for only 2 isolates. These results suggest that MALDI-TOF MS could be a useful tool for routine and fast identification of dermatophytes and Neoscytalidium spp. in clinical mycology laboratories.
87 citations
TL;DR: Matrix-assisted laser desorption/ionization-time of flight mass spectrometry has recently emerged as a powerful technique for identification of microorganisms, changing the workflow of well-established laboratories so that its impact on microbiological diagnostics has been unparalleled.
Abstract: Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) has recently emerged as a powerful technique for identification of microorganisms, changing the workflow of well-established laboratories so that its impact on microbiological diagnostics has been unparalleled. In comparison with conventional identification methods that rely on biochemical tests and require long incubation procedures, MALDI-TOF MS has the advantage of identifying bacteria and fungi directly from colonies grown on culture plates in a few minutes and with simple procedures. Numerous studies on different systems available demonstrate the reliability and accuracy of the method, and new frontiers have been explored besides microbial species level identification, such as direct identification of pathogens from positive blood cultures, subtyping, and drug susceptibility detection.
86 citations
TL;DR: An in depth look into Candida albicans uropathogenesis and distribution of the three most frequent Candida species contributing to urinary tract candidiasis in different countries around the world is taken.
Abstract: Introduction
Urinary tract candidiasis is known as the most frequent nosocomial fungal infection worldwide. Candida albicans is the most common cause of nosocomial fungal urinary tract infections; however, a rapid change in the distribution of Candida species is undergoing. Simultaneously, the increase of urinary tract candidiasis has led to the appearance of antifungal resistant Candida species. In this review, we have an in depth look into Candida albicans uropathogenesis and distribution of the three most frequent Candida species contributing to urinary tract candidiasis in different countries around the world.
86 citations
Additional excerpts
..., Gram-positive cocci, and, among fungi, Candida species [76,77]....
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TL;DR: MALDI-TOF MS has proven to be a useful and rapid identification method for dermatophytes in diagnostic laboratories.
Abstract: In this study we evaluated the suitability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the identification of dermatophytes in diagnostic laboratories. First, a spectral database was built with 108 reference strains belonging to 18 species of the anamorphic genera Epidermophyton, Microsporum and Trichophyton. All strains were well characterized by morphological criteria and ITS sequencing (gold standard). The dendrogram resulting from MALDI-TOF mass spectra was almost identical with the phylogenetic tree based on ITS sequencing. Subsequently, MALDI-TOF MS SuperSpectra were created for the identification of Epidermophyton floccosum, Microsporium audouinii, M. canis, M. gypseum (teleomorph: Arthroderma gypseum), M. gypseum (teleomorph: A. incurvatum), M. persicolor, A. benhamiae (Tax. Entity 3 and Am-Eur. race), T. erinacei, T. interdigitale (anthropophilic and zoophilic populations), T. rubrum/T. violaceum, T. tonsurans and T. terrestre. Because T. rubrum and T. violaceum did not present enough mismatches, a SuperSpectrum covering both species was created, and differentiation between them was done by comparison of eight specific peptide masses. In the second part of this study, MALDI-TOF MS with the newly created SuperSpectra was tested using 141 clinical isolates representing nine species. Analyses were done with 3-day-old cultures. Results were compared to morphological identification and ITS sequencing; 135/141 (95.8%) strains were correctly identified by MALDI-TOF MS compared to 128/141 (90.8%) by morphology. Therefore, MALDI-TOF MS has proven to be a useful and rapid identification method for dermatophytes.
83 citations