Detection and identification of yeasts from formalin-fixed, paraffin-embedded tissue by use of PCR-electrospray ionization mass spectrometry

J Clin Microbiol. 2013 Nov;51(11):3731-4. doi: 10.1128/JCM.01967-13. Epub 2013 Aug 28.

Abstract

Diagnosis of yeast infection is typically accomplished by fungal smear and culture, histopathologic examination, and/or serologic studies. Newer assays based on mass spectrometry may be useful for yeast identification when histologic examination is inconclusive, fungal cultures are not ordered, or cultures fail to yield a causative agent. The purpose of this study was to evaluate the ability of the PLEX-ID broad fungal assay to accurately detect and identify yeasts in formalin-fixed paraffin-embedded (FFPE) tissues. Tissue samples from 78 FFPE specimens with both histopathology and corresponding culture results for a variety of yeasts were tested using the PLEX-ID broad fungal assay. A 40-μm FFPE tissue section from each specimen was digested with proteinase K followed by nucleic acid extraction and PCR using broad-range fungal primers. Yeast DNA in amplified products was identified using electrospray ionization mass spectrometry. Discordant results were resolved by D2 rRNA gene sequencing. PLEX-ID analysis detected yeast DNA in 78.2% (61/78) of the cases, of which 91.8% (56/61) were concordant with culture results. Of the 5 discordant positive results, 4 PLEX-ID results were considered to result from environmental contaminants, while 1 clinically important discrepancy was observed (Blastomyces dermatitidis by culture and Cryptococcus neoformans by PLEX-ID). Sequencing of the discordant sample was unsuccessful. The majority of histopathology results (89.7% [70/78]) correlated with culture results. The PLEX-ID broad fungal assay identifies fungi directly from FFPE tissues and can be a useful adjunct to traditional culture and histopathology tests.

Publication types

  • Evaluation Study

MeSH terms

  • DNA, Fungal / genetics
  • DNA, Fungal / isolation & purification
  • Humans
  • Mycoses / diagnosis*
  • Mycoses / microbiology
  • Pathology, Molecular / methods*
  • Polymerase Chain Reaction / methods*
  • Specimen Handling / methods
  • Spectrometry, Mass, Electrospray Ionization / methods*
  • Tissue Embedding
  • Tissue Fixation
  • Yeasts / genetics
  • Yeasts / isolation & purification*

Substances

  • DNA, Fungal