Identification of clinical isolates of Aspergillus, including cryptic species, by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Abstract

An expanded library of matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been constructed using the spectra generated from 42 clinical isolates and 11 reference strains, including 23 different species from 8 sections (16 cryptic plus 7 noncryptic species). Out of a total of 379 strains of Aspergillus isolated from clinical samples, 179 strains were selected to be identified by sequencing of beta-tubulin or calmodulin genes. Protein spectra of 53 strains, cultured in liquid medium, were used to construct an in-house reference database in the MALDI-TOF MS. One hundred ninety strains (179 clinical isolates previously identified by sequencing and the 11 reference strains), cultured on solid medium, were blindy analyzed by the MALDI-TOF MS technology to validate the generated in-house reference database. A 100% correlation was obtained with both identification methods, gene sequencing and MALDI-TOF MS, and no discordant identification was obtained. The HUVR database provided species level (score of ≥2.0) identification in 165 isolates (86.84%) and for the remaining 25 (13.16%) a genus level identification (score between 1.7 and 2.0) was obtained. The routine MALDI-TOF MS analysis with the new database, was then challenged with 200 Aspergillus clinical isolates grown on solid medium in a prospective evaluation. A species identification was obtained in 191 strains (95.5%), and only nine strains (4.5%) could not be identified at the species level. Among the 200 strains, A. tubingensis was the only cryptic species identified. We demonstrated the feasibility and usefulness of the new HUVR database in MALDI-TOF MS by the use of a standardized procedure for the identification of Aspergillus clinical isolates, including cryptic species, grown either on solid or liquid media.

Discrimination of Aspergillus flavus from Aspergillus oryzae by matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐TOF) mass spectrometry

“…According to MALDI‐TOF MS results, only 18 of 200 isolates identified by sequencing were confirmed as A flavus based on the Bruker score database (log‐score ≥2.0). According to our review of previous studies published since 2011 (Table ), MALDI‐TOF MS scores of ≥ 2.0 were reported as a reliable marker to be used in discrimination of Aspergillus species with the rate ranging from 30.2% to 100% . At the same time, it was indicated that the potential of MALDI‐TOF MS in the identification of cryptic and closely related species in different sections of the Aspergillus genus remained uncertain …”

“…Accumulating evidence suggests that MALDI‐TOF MS is a promising approach to rapid and accurate identification of different clinically relevant pathogens, which was also successfully applied to discriminate among Aspergillus species . In the current study, we analysed the potential of MALDI‐TOF MS to discriminate between A flavus and A oryzae using a set of 121 clinical and 79 environmental A flavus isolates a priori identified as such by sequencing.…”

“…13,14 The aim of the present study was to evaluate the application of MALDI-TOF-MS for the identification of and discrimination between A flavus and A oryzae in clinical and environmental samples and compare its diagnostic power with that of β-tubulin gene sequencing. Accumulating evidence suggests that MALDI-TOF MS is a promising approach to rapid and accurate identification of different clinically relevant pathogens, 10,23,24 which was also successfully applied to discriminate among Aspergillus species. 5,9,11 In the current study, we analysed the potential of MALDI-TOF MS to discriminate between A flavus and A oryzae using a set of 121 clinical and 79 environmental A flavus isolates a priori identified as such by sequencing.…”

Invasive Aspergillosis in Transplant Recipients

“…Matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) technique may be used in the identification of Aspergillus spp. and is a promising tool, particularly for the identification of rare species of Aspergillus [90,91]. This method allows a rapid and reliable identification of the isolate and therefore, an early start of effective antifungal therapy.…”

Klinik Örneklerden İzole Edilen Aspergillus Türlerinin Tanımlanmasında Geleneksel Yöntemler, MALDI-TOF MS ve Dizi Analizi Yöntemlerinin Karşılaştırılması

“…İyonlar kütleleriyle orantılı hız kazanarak detektöre farklı zamanda çarpmaları ile kaydedilen sinyaller proteinlerin kütle spektrumlarını oluşturur. Görüntülenen spektrum, mevcut veri tabanındaki spektrumlarla karşılaştırılarak, hem cins hem de tür bazında tanımlama yapılır 9,10,11,12 .…”