title: Impact of matrix-assisted laser desorption ionization time-of-flight mass spectrometry on the clinical management of patients with Gram-negative bacteremia: a prospective observational study.
abstract: BACKGROUND
  Early identification of pathogens from blood cultures using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry may optimize the choice of empirical antibiotic therapy in the setting of bloodstream infections. We aimed to assess the impact of this new technology on the use of antibiotic treatment in patients with gram-negative bacteremia.
  
  
  METHODS
  We conducted a prospective observational study from January to December 2010 to evaluate the sequential and separate impacts of Gram stain reporting and MALDI-TOF bacterial identification performed on blood culture pellets in patients with gram-negative bacteremia. The primary outcome was the impact of MALDI-TOF on empirical antibiotic choice.
  
  
  RESULTS
  Among 202 episodes of gram-negative bacteremia, Gram stain reporting had an impact in 42 cases (20.8%). MALDI-TOF identification led to a modification of empirical therapy in 71 of all 202 cases (35.1%), and in 16 of 27 cases (59.3%) of monomicrobial bacteremia caused by AmpC-producing Enterobacteriaceae. The most frequently observed impact was an early appropriate broadening of the antibiotic spectrum in 31 of 71 cases (43.7%). In total, 143 of 165 episodes (86.7%) of monomicrobial bacteremia were correctly identified at genus level by MALDI-TOF.
  
  
  CONCLUSIONS
  In a low prevalence area for extended spectrum betalactamases (ESBL) and multiresistant gram-negative bacteria, MALDI-TOF performed on blood culture pellets had an impact on the clinical management of 35.1% of all gram-negative bacteremia cases, demonstrating a greater impact than Gram stain reporting. Thus, MALDI-TOF could become a vital second step beside Gram stain in guiding the empirical treatment of patients with bloodstream infection.
authors.affiliation: Infectious Diseases Service, Institute of Microbiology, Lausanne University Hospital Center and University of Lausanne, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Clerc
authors.forename: Guy
authors.initials: G
authors.lastname: Prod'hom
authors.forename: Christelle
authors.initials: C
authors.lastname: Vogne
authors.forename: Alain
authors.initials: A
authors.lastname: Bizzini
authors.forename: Thierry
authors.initials: T
authors.lastname: Calandra
authors.forename: Gilbert
authors.initials: G
authors.lastname: Greub
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D016470:Bacteremia / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics; D004755:Enterobacteriaceae / Q000201:enzymology*; D004756:Enterobacteriaceae Infections / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D005260:Female; D005840:Gentian Violet / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010619:Phenazines / Q000737:chemistry; D011446:Prospective Studies; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C035863:Gram's stain; D010619:Phenazines; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; D005840:Gentian Violet