title: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification of mycobacteria in routine clinical practice.
abstract: BACKGROUND
  Non-tuberculous mycobacteria recovered from respiratory tract specimens are emerging confounder organisms for the laboratory diagnosis of tuberculosis worldwide. There is an urgent need for new techniques to rapidly identify mycobacteria isolated in clinical practice. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) has previously been proven to effectively identify mycobacteria grown in high-concentration inocula from collections. However, a thorough evaluation of its use in routine laboratory practice has not been performed.
  
  
  METHODS
  We set up an original protocol for the MALDI-TOF MS identification of heat-inactivated mycobacteria after dissociation in Tween-20, mechanical breaking of the cell wall and protein extraction with formic acid and acetonitrile. By applying this protocol to as few as 10(5) colony-forming units of reference isolates of Mycobacterium tuberculosis, Mycobacterium avium, and 20 other Mycobacterium species, we obtained species-specific mass spectra for the creation of a local database. Using this database, our protocol enabled the identification by MALDI-TOF MS of 87 M. tuberculosis, 25 M. avium and 12 non-tuberculosis clinical isolates with identification scores ≥2 within 2.5 hours.
  
  
  CONCLUSIONS
  Our data indicate that MALDI-TOF MS can be used as a first-line method for the routine identification of heat-inactivated mycobacteria. MALDI-TOF MS is an attractive method for implementation in clinical microbiology laboratories in both developed and developing countries.
authors.affiliation: URMITE UMR CNRS 6236 IRD198, Institut Hospitalier Universitaire POLMIT, IFR48, Université de la Méditerranée et Pôle de Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Marseille, France.
authors.forename: Amel
authors.initials: A
authors.lastname: El Khéchine
authors.forename: Carine
authors.initials: C
authors.lastname: Couderc
authors.forename: Christophe
authors.initials: C
authors.lastname: Flaudrops
authors.forename: Didier
authors.initials: D
authors.lastname: Raoult
authors.forename: Michel
authors.initials: M
authors.lastname: Drancourt
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis; D006801:Humans; D009161:Mycobacterium / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001426:Bacterial Proteins