title: Improvement of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification of difficult-to-identify bacteria and its impact in the workflow of a clinical microbiology laboratory.
abstract: This study evaluates matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) capability for the identification of difficult-to-identify microorganisms. A total of 150 bacterial isolates inconclusively identified with conventional phenotypic tests were further assessed by 16S rRNA sequencing and by MALDI-TOF MS following 2 methods: a) a simplified formic acid-based, on-plate extraction and b) performing a tube-based extraction step. Using the simplified method, 29 isolates could not be identified. For the remaining 121 isolates (80.7%), we obtained a reliable identification by MALDI-TOF: in 103 isolates, the identification by 16S rRNA sequencing and MALDI TOF coincided at the species level (68.7% from the total 150 analyzed isolates and 85.1% from the samples with MALDI-TOF result), and in 18 isolates, the identification by both methods coincided at the genus level (12% from the total and 14.9% from the samples with MALDI-TOF results). No discordant results were observed. The performance of the tube-based extraction step allowed the identification at the species level of 6 of the 29 unidentified isolates by the simplified method. In summary, MALDI-TOF can be used for the rapid identification of many bacterial isolates inconclusively identified by conventional methods.
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain. Electronic address: mbelen.rodriguez@iisgm.com.
authors.forename: Belén
authors.initials: B
authors.lastname: Rodríguez-Sánchez
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; Facultad de Medicina, Universidad Complutense de Madrid (UCM), Madrid, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Marín
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Sánchez-Carrillo
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; Facultad de Medicina, Universidad Complutense de Madrid (UCM), Madrid, Spain.
authors.forename: Emilia
authors.initials: E
authors.lastname: Cercenado
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain.
authors.forename: Adrián
authors.initials: A
authors.lastname: Ruiz
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; Facultad de Medicina, Universidad Complutense de Madrid (UCM), Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Rodríguez-Créixems
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; Facultad de Medicina, Universidad Complutense de Madrid (UCM), Madrid, Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Bouza
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000382:microbiology; D001432:Bacteriology; D004269:DNA, Bacterial / Q000235:genetics; D006801:Humans; D007753:Laboratories / Q000458:organization & administration; D058889:Molecular Typing / Q000379:methods*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D057188:Workflow
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: 16S rRNA sequencing; Bacterial identification; Difficult-to-identify bacteria; Laboratory workflow; MALDI-TOF