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Artidentifiering av mögelsvamp med MALDI-TOF MS
Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
2018 (Swedish)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesisAlternative title
Species identification of filamentous fungi with MALDI-TOF MS (English)
Abstract [sv]

Snabb och korrekt artidentifiering är avgörande för effektiv behandling av svampinfektioner, särskilt bland immunsupprimerade patienter. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) används rutinmässigt på kliniska laboratorier för identifiering av karaktäristiska proteinmönster hos bakterier och jästsvampar genom tolkning av proteinspektra i en masspektradatabas för korrekt artidentifiering. Mögelsvamparnas hårda cellvägg och heterogena växtsätt med varierande proteinuttryck beroende på mognadsstadie, försvårar identifiering med MALDI-TOF MS. Metodens tänkbara fördelar mot traditionella metoden mikroskopering är förkortade svarstider, säkrare artidentifiering av fler arter och mindre beroende av subjektiv morfologisk bedömning. Studiens syfte var att undersöka om MALDI-TOF MS kunde anpassas och användas för identifieringen av mögelsvamp i klinisk rutindiagnostik. Fyra referensstammar (Aspergillus niger, A. fumigatus, A.terreus, A.flavus) och ett kliniskt isolat (A.terreus) undersöktes. Preparationsmetoderna (I) fullständig myrsyraextraktion, (II) direktapplicering och (III) suspension i destillerat vatten användes för analys av sporer och frontmycel hos yngre och äldre mögelkulturer. Två olika masspektradatabaser för artidentifiering jämfördes; rutindatabasen BDAL och den specialiserade mögeldatabasen Filamentous Fungi Library. Även plocktekniken av mögelmaterial inför analys med MALDI-TOF MS utvärderades. Vid vissa tillfällen förbättrades artidentifieringen efter extraktion av mögelkulturerna, medan i andra fall var direktapplicering fullt tillräcklig. Mögelmaterial med mycket sporer tenderade ge något fler artidentifieringar i BDAL oavsett kulturernas ålder.  Filamentous Fungi Library tenderade i vissa fall ge bättre resultat jämfört med BDAL för yngre kulturer. Fler studier krävs för att utvärdera och optimera MALDI-TOF MS som metod för artidentifiering av mögelsvamp.

Abstract [en]

Rapid and accurate species identification is crucial for successful treatment of fungal infections, especially among immunosuppressed patients. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is used routinely at clinical laboratories to identify characteristic protein patterns of bacteria and yeast by the interpretation of protein spectra in a database for accurate species identification. The hard cell wall of the mold and the heterogeneous growth with varying protein expression due to maturation, complicates identification with MALDI-TOF MS. The potential benefits of this method compared to microscopy as traditional method are shortened turn-around times, safer species identification of more species that is independent on subjective morphological assessment. The purpose of the study was to investigate whether MALDI-TOF MS could be adapted and used for the identification of molds in clinical routine diagnostics. Four reference strains (Aspergillus niger, A.fumigatus, A.terreus, A.flavus) and a clinical isolate (A.terreus) were examined. The preparation methods (I) complete formic acid extraction, (II) direct application and (III) suspension in distilled water were used for analysis of spores and frontmycelium from younger and older mold cultures. Two different masspektradatabases for species identification were compared; routine database BDAL and the specialized mold database, Filamentous Fungi Library. Also the collecting technique of mold prior to analysis with MALDI-TOF MS was evaluated. Sometimes, the species identification improved after extraction of mold cultures, while in other cases direct application was sufficient. Cultures with a lot of spores tended to give slightly more species identifications in BDAL regardless of the age of cultures. Filamentous Fungi Library, in some cases, tended to improve the performance compared to BDAL for younger cultures. More studies are required to evaluate and optimize MALDI-TOF MS as a method of mold identification.

Place, publisher, year, edition, pages
2018. , p. 22
Keywords [en]
Filamentous fungi, species identification, MALDI-TOF MS, database
Keywords [sv]
Mögelsvamp, artidentifiering, MALDI-TOF MS, databas
National Category
Clinical Laboratory Medicine
Identifiers
URN: urn:nbn:se:lnu:diva-80166OAI: oai:DiVA.org:lnu-80166DiVA, id: diva2:1285217
External cooperation
Landstinget i Kalmar
Subject / course
Biomedical Laboratory Science
Educational program
Biomedical Laboratory Science Programme, 180 credits
Supervisors
Examiners
Available from: 2019-02-04 Created: 2019-02-03 Last updated: 2019-02-25Bibliographically approved

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