title: Mould routine identification in the clinical laboratory by matrix-assisted laser desorption ionization time-of-flight mass spectrometry.
abstract: BACKGROUND
  MALDI-TOF MS recently emerged as a valuable identification tool for bacteria and yeasts and revolutionized the daily clinical laboratory routine. But it has not been established for routine mould identification. This study aimed to validate a standardized procedure for MALDI-TOF MS-based mould identification in clinical laboratory.
  
  
  METHODS
  First, pre-extraction and extraction procedures were optimized. With this standardized procedure, a 143 mould strains reference spectra library was built. Then, the mould isolates cultured from sequential clinical samples were prospectively subjected to this MALDI-TOF MS based-identification assay. MALDI-TOF MS-based identification was considered correct if it was concordant with the phenotypic identification; otherwise, the gold standard was DNA sequence comparison-based identification.
  
  
  RESULTS
  The optimized procedure comprised a culture on sabouraud-gentamicin-chloramphenicol agar followed by a chemical extraction of the fungal colonies with formic acid and acetonitril. The identification was done using a reference database built with references from at least four culture replicates. For five months, 197 clinical isolates were analyzed; 20 were excluded because they were not identified at the species level. MALDI-TOF MS-based approach correctly identified 87% (154/177) of the isolates analyzed in a routine clinical laboratory activity. It failed in 12% (21/177), whose species were not represented in the reference library. MALDI-TOF MS-based identification was correct in 154 out of the remaining 156 isolates. One Beauveria bassiana was not identified and one Rhizopus oryzae was misidentified as Mucor circinelloides.
  
  
  CONCLUSIONS
  This work's seminal finding is that a standardized procedure can also be used for MALDI-TOF MS-based identification of a wide array of clinically relevant mould species. It thus makes it possible to identify moulds in the routine clinical laboratory setting and opens new avenues for the development of an integrated MALDI-TOF MS-based solution for the identification of any clinically relevant microorganism.
authors.affiliation: Laboratoire de Parasitologie-Mycologie, CHU Timone, Université de la Méditerranée, Marseille, France. carole.cassagne@ap-hm.fr
authors.forename: Carole
authors.initials: C
authors.lastname: Cassagne
authors.forename: Stéphane
authors.initials: S
authors.lastname: Ranque
authors.forename: Anne-Cécile
authors.initials: AC
authors.lastname: Normand
authors.forename: Patrick
authors.initials: P
authors.lastname: Fourquet
authors.forename: Sandrine
authors.initials: S
authors.lastname: Thiebault
authors.forename: Chantal
authors.initials: C
authors.lastname: Planard
authors.forename: Marijke
authors.initials: M
authors.lastname: Hendrickx
authors.forename: Renaud
authors.initials: R
authors.lastname: Piarroux
mesh_terms: D019411:Clinical Laboratory Techniques / Q000379:methods*; D005658:Fungi / Q000302:isolation & purification*; D006801:Humans; D012015:Reference Standards; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*