title: Direct identification of microorganisms from positive blood cultures by MALDI-TOF MS using an in-house saponin method.
abstract: OBJECTIVE
  Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a fast and reliable method for the identification of bacteria. A MALDI Sepsityper kit is generally used to prepare samples obtained directly from culture bottles. However, the relatively high cost of this kit is a major obstacle to introducing this method into routine clinical use. In this study, the accuracies of three different preparation methods for rapid direct identification of bacteria from positive blood culture bottles by MALDI-TOF MS analysis were compared.
  
  
  METHODS
  In total, 195 positive bottles were included in this study.
  
  
  RESULTS
  Overall, 78.5%, 68.7%, and 76.4% of bacteria were correctly identified to the genus level (score ≥1.7) directly from positive blood cultures using the Sepsityper, centrifugation, and saponin methods, respectively. The identification rates using the Sepsityper and saponin methods were significantly higher than that using the centrifugation method (Sepsityper vs. centrifugation, p<0.001; saponin vs. centrifugation, p=0.003).
  
  
  CONCLUSIONS
  These results suggest that the saponin method is superior to the centrifugation method and comparable to the Sepsityper method in the accuracy of rapid bacterial identification directly from blood culture bottles, and could be a less expensive alternative to the Sepsityper method.
authors.affiliation: Department of Clinical Laboratory, Kyorin University School of Medicine, Tokyo, Japan; Department of Microbiology, Tokyo Medical University, Tokyo, Japan. Electronic address: yonetani@ks.kyorin-u.ac.jp.
authors.forename: Shota
authors.initials: S
authors.lastname: Yonetani
authors.affiliation: Department of Clinical Laboratory, Kyorin University School of Medicine, Tokyo, Japan; Department of Laboratory Medicine, Kyorin University School of Medicine, Tokyo, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ohnishi
authors.affiliation: Department of Microbiology, Tokyo Medical University, Tokyo, Japan.
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Ohkusu
authors.affiliation: Department of Microbiology, Tokyo Medical University, Tokyo, Japan; Department of Infection Control, Tokyo Medical University Hospital, Tokyo, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Clinical Laboratory, Kyorin University School of Medicine, Tokyo, Japan; Department of Laboratory Medicine, Kyorin University School of Medicine, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D016470:Bacteremia / Q000382:microbiology*; D001431:Bacteriological Techniques / Q000379:methods; D000071997:Blood Culture; D006801:Humans; D012503:Saponins / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D012503:Saponins
keywords: Blood culture; Centrifugation; MALDI-TOF MS; Saponin; Sepsityper