title: Comparison of the Bruker Biotyper and VITEK MS Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Systems Using a Formic Acid Extraction Method to Identify Common and Uncommon Yeast Isolates.
abstract: BACKGROUND
  Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows rapid and accurate identification of clinical yeast isolates. In-tube formic acid/acetonitrile (FA/ACN) extraction is recommended prior to the analysis with MALDI Biotyper, but the direct on-plate FA extraction is simpler. We compared the Biotyper with the VITEK MS for the identification of various clinically relevant yeast species, focusing on the use of the FA extraction method.
  
  
  METHODS
  We analyzed 309 clinical isolates of 42 yeast species (four common Candida species, Cryptococcus neoformans, and 37 uncommon yeast species) using the Biotyper and VITEK MS systems. FA extraction was used initially for all isolates. If 'no identification' result was obtained following the initial FA extraction, these samples were then retested by using FA (both systems, additive FA) or FA/ACN (Biotyper only, additive FA/ACN) extraction. These results were compared with those obtained by sequence-based identification.
  
  
  RESULTS
  Both systems correctly identified all 158 isolates of the four common Candida species after the initial FA extraction. The Biotyper correctly identified 8.7%, 30.4%, and 100% of 23 C. neoformans isolates after performing initial FA, additive FA, and FA/ACN extractions, respectively, while VITEK MS identified all C. neoformans isolates after the initial FA extraction. Both systems had comparable identification rates of 37 uncommon yeast species (128 isolates), following the initial FA (Biotyper, 74.2%; VITEK MS, 73.4%) or additive FA (Biotyper, 82.0%; VITEK MS, 73.4%).
  
  
  CONCLUSIONS
  The identification rate of most common and uncommon yeast isolates is comparable between simple FA extraction/Biotyper method and VITEK MS methods, but FA/ACN extraction is necessary for C. neoformans identification by Biotyper.
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Hyun Seung
authors.initials: HS
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea. shinjh@chonnam.ac.kr.
authors.forename: Jong Hee
authors.initials: JH
authors.lastname: Shin
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Choi
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Won
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Seung Jung
authors.initials: SJ
authors.lastname: Kee
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Myung Geun
authors.initials: MG
authors.lastname: Shin
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Soon Pal
authors.initials: SP
authors.lastname: Suh
mesh_terms: D002175:Candida / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D003455:Cryptococcus neoformans / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D005561:Formates / Q000737:chemistry*; D052616:Solid Phase Extraction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D015003:Yeasts / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D005561:Formates; C030544:formic acid
keywords: Biotyper; Candida; Formic acid extraction; Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS); VITEK MS; Yeast