title: Complexities associated with the molecular and proteomic identification of Paecilomyces species in the clinical mycology laboratory.
abstract: Paecilomyces species are emerging fungal pathogens. Morphological identifications are complicated by similarities among the members of the P. variotii complex as well as to some Rasamsonia and Hamigera species. The purpose of this study was to compare matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) with molecular diagnostic standards (i.e., multilocus DNA sequencing of the internal transcribed spacer regions 1 and 2, D1/D2 regions, and part of the β-tubulin gene) for the identification of Paecilomyces spp. encountered in two clinical mycology laboratories. A total of 77 clinical isolates identified morphologically as P. variotii (n = 21), P. lilacinus (n = 52), and Paecilomyces spp. not otherwise specified (n = 4) were included. In accord with the most recent taxonomy, all P. lilacinus isolates were confirmed as Purpureocillium lilacinum by both sequencing and MALDI-TOF MS. Fungi phenotypically resembling P. variotii or Paecilomyces spp. were identified by molecular techniques as P. variotii sensu stricto (n = 12), P. formosus (n = 3), P. dactylethromorphus (n = 3), Rasamsonia argillacea (n = 4), or R. piperina (n = 1) and at the genus level as an isolate of a Hamigera sp. and a Paecilomyces sp. There was 92.2% (71/77) agreement between the molecular and proteomic methods only after supplementation of the MALDI-TOF MS database with type strains. Paecilomyces variotii-like organisms required multilocus DNA interrogations for differentiation and account for all of the fungi whose identification was missed by MALDI-TOF MS. Overall, MALDI-TOF MS was a rapid and reliable alternative to multilocus sequencing. However, significant augmentation of the commercially available database was required to reproducibly identify this group of important human pathogens.
authors.affiliation: Department of Pathology, University of Utah, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA adam.barker@path.utah.edu.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Barker
authors.affiliation: Department of Medicine/Infectious Diseases, Duke University Medical Center, Durham, NC, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Horan
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA.
authors.forename: E Susan
authors.initials: ES
authors.lastname: Slechta
authors.affiliation: Department of Medicine/Infectious Diseases, Duke University Medical Center, Durham, NC, USA.
authors.forename: Barbara D
authors.initials: BD
authors.lastname: Alexander
authors.affiliation: Department of Medicine and Department of Pathology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Kimberly E
authors.initials: KE
authors.lastname: Hanson
mesh_terms: D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D007753:Laboratories; D058885:Multilocus Sequence Typing; D016533:Mycological Typing Techniques; D009181:Mycoses / Q000382:microbiology*; D010143:Paecilomyces / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D010802:Phylogeny; D025341:Principal Component Analysis; D040901:Proteomics; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D005656:Fungal Proteins
keywords: Paecilomyces variotii; Purpureocillium lilacinum; filamentous fungi; fungal infections; matrix-assisted laser desorption–ionization time-of-flight mass spectrometry