title: Direct Identification of Aerobic Bacteria by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry Is Accurate and Robust.
abstract: BACKGROUND
  Bacterial identification in the clinical laboratory can be laborious and expensive. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a rapid and cost-effective diagnostic tool for the identification of organisms routinely found in the microbiology laboratory. The objective of this study was to demonstrate that identification of aerobic Gram-positive and Gram-negative organisms could be performed accurately and efficiently by MALDI-TOF MS and the Bruker Biotyper system without the use of time-consuming extraction methodologies.
  
  
  METHODS
  Isolates previously recovered by routine culture and workup from clinical specimens were cultured to appropriate media, identified directly by MALDI-TOF MS, and compared to results from various biochemical identification methods.
  
  
  RESULTS
  Using the direct-smear method, 99.5% and 98.0% of aerobic Gram-negative and Gram-positive bacteria, respectively, were identified to the genus level. At a score of ≥1.9, 97.6% Gram-negative organisms and 94.6% Gram-positive organisms were correctly identified to the species level by direct-smear method. Only 1.1% of isolates required further reflex to direct-plate extraction. The direct-smear method proved to be robust, as various growth temperatures, media, culture age, and different operators had no notable impact on the bacterial identification rate.
  
  
  CONCLUSIONS
  The direct-smear method is an accurate and time-saving method for routine species-level bacterial identification.
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California.
authors.forename: Javier
authors.initials: J
authors.lastname: Mestas
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California.
authors.forename: Teephany
authors.initials: T
authors.lastname: Quias
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, California. jdienbard@chla.usc.edu.|Keck School of Medicine at the University of Southern California, Los Angeles, California. jdienbard@chla.usc.edu.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Dien Bard
mesh_terms: D001420:Bacteria, Aerobic / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000175:diagnosis*; D001431:Bacteriological Techniques / Q000379:methods; D016009:Chi-Square Distribution; D064790:Clinical Laboratory Services; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013696:Temperature; D013997:Time Factors
keywords: Gram-negative; Gram-positive; MALDI-TOF MS; bacteria identification; direct smear; extraction