title: Identification of mycobacterium spp. and nocardia spp. from solid and liquid cultures by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS).
abstract: Identification of microorganisms by MALDI-TOF MS has been widely accepted in clinical microbiology. However, for Mycobacterium spp. and Nocardia spp. such identification has not yet reached the optimal level of routine testing. Here we describe the development of an identification tool for 49 and 15 species of Mycobacterium spp. and Nocardia spp., respectively. During database construction, a number of ambiguous reference identifications were revealed and corrected via molecular analyses. Eventually, more than 2000 individual mass spectra acquired from 494 strains were included in a reference database and subjected to bio-statistical analyses. This led to correct species identification and correct combination of species into several complexes or groups, such as the Mycobacterium tuberculosis complex. With the Advanced Spectrum Classifier algorithm, class-specific bin weights were determined and tested by cross-validation experiments with good results. When challenged with independent isolates, overall identification performance was 90% for identification of Mycobacterium spp. and 88% for Nocardia spp. However, for a number of Mycobacterium sp. isolates, no identification could be achieved and in most cases, this could be attributed to the production of polymers that masked the species-specific protein peak patterns. For the species where >20 isolates were tested, correct identification reached 95% or higher. With the current spectral database, the identification of Mycobacterium spp. and Nocardia spp. by MALDI-TOF MS can be performed in routine clinical diagnostics although in some complicated cases verification by sequencing remains mandatory.
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Victoria
authors: V
authors: Girard
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Sandrine
authors: S
authors: Mailler
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Martin
authors: M
authors: Welker
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Maud
authors: M
authors: Arsac
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Béatrice
authors: B
authors: Cellière
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Pierre-Jean
authors: PJ
authors: Cotte-Pattat
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Sonia
authors: S
authors: Chatellier
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France.
authors: Géraldine
authors: G
authors: Durand
authors: Hôpitaux Universitaires de Genève, Laboratoire de Bactériologie, Rue Gabrielle Perret Gentil 4, 1211, Geneva 14, Switzerland.
authors: Anne-Marie
authors: AM
authors: Béni
authors: Hôpitaux Universitaires de Genève, Laboratoire de Bactériologie, Rue Gabrielle Perret Gentil 4, 1211, Geneva 14, Switzerland.
authors: Jacques
authors: J
authors: Schrenzel
authors: bioMérieux Inc., Microbiology R&D, 100 Rodolphe St, Durham, NC, 27712, USA.
authors: Elizabeth
authors: E
authors: Miller
authors: bioMérieux Inc., Microbiology R&D, 100 Rodolphe St, Durham, NC, 27712, USA.
authors: Rahima
authors: R
authors: Dussoulier
authors: bioMérieux Inc., Microbiology R&D, 100 Rodolphe St, Durham, NC, 27712, USA.
authors: W Michael
authors: WM
authors: Dunne
authors: Clinical Microbiology Laboratory, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA; Keck School of Medicine, University of Southern California, 1975 Zonal Avenue, Los Angeles, CA, 90033, USA.
authors: Susan
authors: S
authors: Butler-Wu
authors: Banner University Medical Center, 1111 E. McDowell Rd., Phoenix, AZ, 85006, USA.
authors: Michael A
authors: MA
authors: Saubolle
authors: Banner University Medical Center, 1111 E. McDowell Rd., Phoenix, AZ, 85006, USA.
authors: Den
authors: D
authors: Sussland
authors: Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329-4027, USA.
authors: Melissa
authors: M
authors: Bell
authors: bioMérieux, Microbiology R&D, Route de Port Michaud, 38390, La Balme, Les Grottes, France. Electronic address: alex.vanbelkum@biomerieux.com.
authors: Alex
authors: A
authors: van Belkum
authors: bioMérieux Inc., Microbiology R&D, 100 Rodolphe St, Durham, NC, 27712, USA.
authors: Parampal
authors: P
authors: Deol
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D003470:Culture Media; D006801:Humans; D009161:Mycobacterium / Q000737:chemistry / Q000302:isolation & purification*; D009164:Mycobacterium Infections / Q000382:microbiology; D009615:Nocardia / Q000737:chemistry / Q000302:isolation & purification*; D009617:Nocardia Infections / Q000382:microbiology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D003470:Culture Media
keywords: MALDI TOF MS; Mycobacteria; Nocardiae; Solid and liquid cultures