title: The optimization and validation of the Biotyper MALDI-TOF MS database for the identification of Gram-positive anaerobic cocci.
abstract: Gram-positive anaerobic cocci (GPAC) account for 24%-31% of the anaerobic bacteria isolated from human clinical specimens. At present, GPAC are under-represented in the Biotyper MALDI-TOF MS database. Profiles of new species have yet to be added. We present the optimization of the matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) database for the identification of GPAC. Main spectral profiles (MSPs) were created for 108 clinical GPAC isolates. Identity was confirmed using 16S rRNA gene sequencing. Species identification was considered to be reliable if the sequence similarity with its closest relative was ≥98.7%. The optimized database was validated using 140 clinical isolates. The 16S rRNA sequencing identity was compared with the MALDI-TOF MS result. MSPs were added from 17 species that were not yet represented in the MALDI-TOF MS database or were under-represented (fewer than five MSPs). This resulted in an increase from 53.6% (75/140) to 82.1% (115/140) of GPAC isolates that could be identified at the species level using MALDI-TOF MS. An improved log score was obtained for 51.4% (72/140) of the strains. For strains with a sequence similarity <98.7% with their closest relative (n = 5) or with an inconclusive sequence identity (n = 4), no identification was obtained by MALDI-TOF MS or in the latter case an identity with one of its relatives. For some species the MSP of the type strain was not part of the confined cluster of the corresponding clinical isolates. Also, not all species formed a homogeneous cluster. It emphasizes the necessity of adding sufficient MSPs of human clinical isolates.
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Centre Groningen, The Netherlands. Electronic address: a.c.m.veloo@umcg.nl.
authors.forename: A C M
authors.initials: AC
authors.lastname: Veloo
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Centre Groningen, The Netherlands.
authors.forename: E D
authors.initials: ED
authors.lastname: de Vries
authors.affiliation: Centre Hospitalier Universitaire de Montpellier, Hôpital Arnaud de Villeneuve, Laboratoire de Bactériologie, Montpellier, France; Université Montpellier 1, UMR5119 ECOSYM, Equipe Pathogènes Hydriques Santé Environnements, UMR 5569 Hydrosciences, UFR Pharmacie, Montpellier, France.
authors.forename: H
authors.initials: H
authors.lastname: Jean-Pierre
authors.affiliation: Department of Clinical Microbiology, Odense University Hospital, Odense, Denmark.
authors.forename: U S
authors.initials: US
authors.lastname: Justesen
authors.affiliation: UK Anaerobe Reference Unit, Public Health Wales Microbiology, Cardiff, UK.
authors.forename: T
authors.initials: T
authors.lastname: Morris
authors.affiliation: Institute of Clinical Microbiology, University of Szeged, Hungary.
authors.forename: E
authors.initials: E
authors.lastname: Urban
authors.affiliation: Department of Microbiology and Infection Control, Universitair Ziekenhuis Brussel, Brussels, Belgium.
authors.forename: I
authors.initials: I
authors.lastname: Wybo
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Centre Groningen, The Netherlands; Department of Dentistry and Oral Hygiene, University of Groningen, University Medical Centre Groningen, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: van Winkelhoff
mesh_terms: D001421:Bacteria, Anaerobic / Q000145:classification* / Q000235:genetics; D015373:Bacterial Typing Techniques; D016208:Databases, Factual; D006094:Gram-Positive Bacteria / Q000145:classification* / Q000235:genetics; D006801:Humans; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D015203:Reproducibility of Results; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D012336:RNA, Ribosomal, 16S
keywords: Database; European Network for the Rapid Identification of Anaerobes; Gram-positive anaerobic cocci; Identification; Matrix-assisted laser desorption–ionization time-of-flight mass spectrometry; Optimization