title: Identification and cluster analysis of Streptococcus pyogenes by MALDI-TOF mass spectrometry.
abstract: BACKGROUND
  Whole-cell matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has been successfully applied for bacterial identification and typing of many pathogens. The fast and reliable qualities of MALDI-TOF MS make it suitable for clinical diagnostics. MALDI-TOF MS for the identification and cluster analysis of Streptococcus pyogenes, however, has not been reported. The goal of our study was to evaluate this approach for the rapid identification and typing of S. pyogenes.
  
  
  METHODS
  65 S. pyogenes isolates were obtained from the hospital. The samples were prepared and MALDI-TOF MS measurements were conducted as previously reported. Identification of unknown spectra was performed via a pattern recognition algorithm with a reference spectra and a dendrogram was constructed using the statistical toolbox in Matlab 7.1 integrated in the MALDI Biotyper 2.0 software.
  
  
  RESULTS
  For identification, 61 of 65 S. pyogenes isolates could be identified correctly by MALDI-TOF MS with BioType 2.0 when compared to biochemical identification (API Strep), with an accuracy of 93.85%. In clustering analysis, 44 of 65 isolates were in accordance with those established by M typing, with a matching rate of 67.69%. When only the M type prevalence in China was considered, 41 of 45 isolates were in agreement with M typing, with a matching rate of 91.1%.
  
  
  CONCLUSIONS
  It was here shown that MALDI-TOF MS with Soft Biotype 2.0 and its database could facilitate rapid identification of S. pyogenes. It may present an attractive alternative to traditional biochemical methods of identification. However, for classification, more isolates and advances in the MALDI-TOF MS technology are needed to improve accuracy.
authors.affiliation: National Center of Biomedical Analysis, Beijing, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.forename: Na
authors.initials: N
authors.lastname: Zhou
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.forename: Huaijie
authors.initials: H
authors.lastname: Hao
authors.forename: Lin
authors.initials: L
authors.lastname: Kang
authors.forename: Yuling
authors.initials: Y
authors.lastname: Zheng
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Jiang
authors.forename: Hua
authors.initials: H
authors.lastname: Jiang
mesh_terms: D015373:Bacterial Typing Techniques / Q000191:economics / Q000379:methods*; D016000:Cluster Analysis; D006801:Humans; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000191:economics / Q000379:methods*; D013290:Streptococcal Infections / Q000175:diagnosis*; D013297:Streptococcus pyogenes / Q000145:classification* / Q000302:isolation & purification*