title: MALDI-TOF/MS identification of species from the Acinetobacter baumannii (Ab) group revisited: inclusion of the novel A. seifertii and A. dijkshoorniae species.
abstract: OBJECTIVE
  Rapid identification of Acinetobacter species is critical as members of the A. baumannii (Ab) group differ in antibiotic susceptibility and clinical outcomes. A. baumannii, A. pittii, and A. nosocomialis can be identified by MALDI-TOF/MS, while the novel species A. seifertii and A. dijkshoorniae cannot. Low identification rates for A. nosocomialis also have been reported. We evaluated the use of MALDI-TOF/MS to identify isolates of A. seifertii and A. dijkshoorniae and revisited the identification of A. nosocomialis to update the Bruker taxonomy database.
  
  
  METHODS
  Species characterization was performed by rpoB-clustering and MLSA. MALDI-TOF/MS spectra were recovered from formic acid/acetonitrile bacterial extracts overlaid with α-cyano-4-hydroxy-cinnamic acid matrix on a MicroflexLT in linear positive mode and 2000-20 000 m/z range mass. Spectra were examined with the ClinProTools v2.2 software. Mean spectra (MSP) were created with the BioTyper software.
  
  
  RESULTS
  Seventy-eight Acinetobacter isolates representative of the Ab group were used to calculate the average spectra/species and generate pattern recognition models. Species-specific peaks were identified for all species, and MSPs derived from three A. seifertii, two A. dijkshoorniae, and two A. nosocomialis strains were added to the Bruker taxonomy database, allowing successful identification of all isolates using spectra from either bacterial extracts or direct colonies, resulting in a positive predictive value (PPV) of 99.6% (777/780) and 96.8% (302/312), respectively.
  
  
  CONCLUSIONS
  The use of post-processing data software identified statistically significant species-specific peaks to generate reference signatures for rapid accurate identification of species within the Ab group, providing relevant information for the clinical management of Acinetobacter infections.
authors.affiliation: Department of Clinical Microbiology and ISGlobal- Barcelona Ctr. Int. Health Res. CRESIB, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Marí-Almirall
authors.affiliation: Department of Clinical Microbiology and ISGlobal- Barcelona Ctr. Int. Health Res. CRESIB, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Cosgaya
authors.affiliation: Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany; German Centre for Infection Research (DZIF), Partner site Bonn-Cologne, Germany.
authors.forename: P G
authors.initials: PG
authors.lastname: Higgins
authors.affiliation: Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Department of Microbial and Molecular Systems (M2S), KU Leuven, Sint-Katelijne-Waver, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Van Assche
authors.affiliation: Department of Clinical Microbiology, School of Medicine, Adnan Menderes University, Aydin, Turkey.
authors.forename: M
authors.initials: M
authors.lastname: Telli
authors.affiliation: BCCM/LMG Bacteria Collection & Laboratory of Microbiology, Faculty of Sciences, Ghent University, Ghent, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Huys
authors.affiliation: Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Department of Microbial and Molecular Systems (M2S), KU Leuven, Sint-Katelijne-Waver, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Lievens
authors.affiliation: Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany; German Centre for Infection Research (DZIF), Partner site Bonn-Cologne, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Seifert
authors.affiliation: Department of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Dijkshoorn
authors.affiliation: Department of Clinical Microbiology and ISGlobal- Barcelona Ctr. Int. Health Res. CRESIB, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain. Electronic address: Ignasi.roca@isglobal.org.
authors.forename: I
authors.initials: I
authors.lastname: Roca
authors.affiliation: Department of Clinical Microbiology and ISGlobal- Barcelona Ctr. Int. Health Res. CRESIB, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Vila
mesh_terms: D000150:Acinetobacter / Q000737:chemistry / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D000151:Acinetobacter Infections / Q000175:diagnosis*; D001431:Bacteriological Techniques / Q000379:methods*; D016000:Cluster Analysis; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D006801:Humans; D058885:Multilocus Sequence Typing; D011237:Predictive Value of Tests; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit
keywords: Acinetobacter; ClinProTools; MALDI-TOF/MS; MLSA; rpoB