title: Use of MALDI Biotyper plus ClinProTools mass spectra analysis for correct identification of Streptococcus pneumoniae and Streptococcus mitis/oralis.
abstract: BACKGROUND
  Differentiation of Streptococcus pneumoniae from other viridans group streptococci is well known to be challenging in clinical laboratories. Matrix assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF MS) had been reported to be a good alternative for Streptococcus species level identification. However, differentiation of S. pneumoniae from other Streptococcus mitis group organisms was found to be problematic using the Bruker MALDI Biotyper system.
  
  
  METHODS
  This study used the Bruker MALDI Biotyper system in addition to a mass spectra model analysis generated by 10 reference strains of S. pneumoniae, 8 strains of S. mitis and 2 strains of S. oralis in the ClinProTools to identify 28 clinical isolates of S. pneumoniae and 47 isolates of S. mitis/oralis. The results were compared with those generated by the MALDI Biotyper system alone.
  
  
  RESULTS
  The percentages of correct species level identification using the MALDI Biotyper system alone and the direct transfer and extraction method were 66.7% (50/75) and 70.7% (53/75), respectively. With the additional ClinProTools mass spectra analysis, the percentages of correct identification by the direct transfer and extraction method increased to 85.3% (64/75) and 100% (75/75), respectively. This new workflow significantly improved the accuracy of S. pneumoniae and S. mitis/oralis identification.
  
  
  CONCLUSIONS
  The additional ClinProTools mass spectra analysis with extraction method after MALDI Biotyper identification significantly improved the accuracy of identification among S. pneumoniae, S. oralis and S. mitis. The extra 15 min processing time of spectra analysis should be affordable in most clinical laboratories. We suggest that the same approach could be further explored in handling other bacterial species with high similarities.
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Jonathan H K
authors.initials: JH
authors.lastname: Chen
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Kevin K K
authors.initials: KK
authors.lastname: She
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Oi-Ying
authors.initials: OY
authors.lastname: Wong
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Jade L L
authors.initials: JL
authors.lastname: Teng
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Wing-Cheong
authors.initials: WC
authors.lastname: Yam
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Susanna K P
authors.initials: SK
authors.lastname: Lau
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Patrick C Y
authors.initials: PC
authors.lastname: Woo
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China Infection Control Team, Queen Mary Hospital, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Vincent C C
authors.initials: VC
authors.lastname: Cheng
authors.affiliation: Department of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong Special Administrative Region, Hong Kong, China.
authors.forename: Kwok-Yung
authors.initials: KY
authors.lastname: Yuen
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification*; D004867:Equipment Design; D040901:Proteomics / Q000295:instrumentation* / Q000592:standards; D012015:Reference Standards; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation* / Q000592:standards; D034361:Streptococcus mitis / Q000145:classification / Q000302:isolation & purification*; D019533:Streptococcus oralis / Q000145:classification / Q000302:isolation & purification*; D013296:Streptococcus pneumoniae / Q000145:classification / Q000302:isolation & purification*; D013997:Time Factors; D057188:Workflow
chemical_list: D001426:Bacterial Proteins
keywords: DIAGNOSTICS; MICROBIOLOGY; STREPTOCOCCUS