title: Performances of the Vitek MS matrix-assisted laser desorption ionization-time of flight mass spectrometry system for rapid identification of bacteria in routine clinical microbiology.
abstract: Rapid and cost-effective matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)-based systems will replace conventional phenotypic methods for routine identification of bacteria. We report here the first evaluation of the new MALDI-TOF MS-based Vitek MS system in a large clinical microbiology laboratory. This system uses an original spectrum classifier algorithm and a specific database designed for the identification of clinically relevant species. We have tested 767 routine clinical isolates representative of 50 genera and 124 species. Vitek MS-based identifications were performed by means of a single deposit on a MALDI disposable target without any prior extraction step and compared with reference identifications obtained mainly with the VITEK2 phenotypic system; if the identifications were discordant, molecular techniques provided reference identifications. The Vitek MS system provided 96.2% correct identifications to the species level (86.7%), to the genus level (8.2%), or within a range of species belonging to different genera (1.3%). Conversely, 1.3% of isolates were misidentified and 2.5% were unidentified, partly because the species was not included in the database; a second deposit provided a successful identification for 0.8% of isolates unidentified with the first deposit. The Vitek MS system is a simple, convenient, and accurate method for routine bacterial identification with a single deposit, considering the high bacterial diversity studied and as evidenced by the low prevalence of species without correct identification. In addition to a second deposit in uncommon cases, expanding the spectral database is expected to further enhance performances.
authors.affiliation: Laboratoire de Bactériologie-Hygiène, Institut Fédératif de Biologie, Centre Hospitalo-Universitaire, Toulouse, France. dubois.d@chu-toulouse.fr
authors.forename: Damien
authors.initials: D
authors.lastname: Dubois
authors.forename: Marion
authors.initials: M
authors.lastname: Grare
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Prere
authors.forename: Christine
authors.initials: C
authors.lastname: Segonds
authors.forename: Nicole
authors.initials: N
authors.lastname: Marty
authors.forename: Eric
authors.initials: E
authors.lastname: Oswald
mesh_terms: D001419:Bacteria / Q000737:chemistry* / Q000145:classification* / Q000302:isolation & purification; D001424:Bacterial Infections / Q000175:diagnosis*; D001431:Bacteriological Techniques / Q000379:methods*; D003951:Diagnostic Errors; D006801:Humans; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*