title: Phenotypic identification of Porphyromonas gingivalis validated with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
abstract: OBJECTIVE
  Porphyromonas gingivalis is a major bacterial pathogen in human periodontitis. This study used matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry to assess the accuracy of a rapid phenotypic identification scheme for detection of cultivable P. gingivalis in human subgingival plaque biofilms.
  
  
  METHODS
  A total of 314 fresh cultivable subgingival isolates from 38 adults with chronic periodontitis were presumptively identified on anaerobically-incubated enriched Brucella blood agar primary isolation plates as P. gingivalis based on dark-pigmented colony morphology, lack of a brick-red autofluorescence reaction under long-wave ultraviolet light, and a positive CAAM fluorescence test for trypsin-like enzyme activity. Each presumptive P. gingivalis isolate, and a panel of other human subgingival bacterial species, were subjected to MALDI-TOF mass spectrometry analysis using a benchtop mass spectrometer equipped with software containing mass spectra for P. gingivalis in its reference library of bacterial protein profiles. A MALDI-TOF mass spectrometry log score of ≥1.7 was required for species identification of the subgingival isolates.
  
  
  RESULTS
  All 314 (100%) presumptive P. gingivalis subgingival isolates were confirmed as P. gingivalis with MALDI-TOF mass spectrometry analysis (Cohen's kappa coefficient = 1.0). MALDI-TOF mass spectrometry log scores between 1.7 and 1.9, and ≥2.0, were found for 92 (29.3%) and 222 (70.7%), respectively, of the presumptive P. gingivalis clinical isolates. No other tested bacterial species was identified as P. gingivalis by MALDI-TOF mass spectrometry.
  
  
  CONCLUSIONS
  Rapid phenotypic identification of cultivable P. gingivalis in human subgingival biofilm specimens was found to be 100% accurate with MALDI-TOF mass spectrometry. These findings provide validation for the continued use of P. gingivalis research data based on this species identification methodology.
authors.affiliation: Department of Periodontology and Oral Implantology, Oral Microbiology Testing Service Laboratory, Temple University School of Dentistry, Philadelphia, PA, 19140, USA; Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, PA, 19140, USA. Electronic address: trams@temple.edu.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Rams
authors.affiliation: Department of Periodontology and Oral Implantology, Oral Microbiology Testing Service Laboratory, Temple University School of Dentistry, Philadelphia, PA, 19140, USA.
authors.forename: Jacqueline D
authors.initials: JD
authors.lastname: Sautter
authors.affiliation: Department of Periodontology and Oral Implantology, Oral Microbiology Testing Service Laboratory, Temple University School of Dentistry, Philadelphia, PA, 19140, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Getreu
authors.affiliation: Department of Medical Microbiology, and Center for Dentistry and Oral Hygiene, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Arie J
authors.initials: AJ
authors.lastname: van Winkelhoff
mesh_terms: D000328:Adult; D001426:Bacterial Proteins / Q000032:analysis / Q000302:isolation & purification; D016866:Bacteroidaceae Infections / Q000382:microbiology*; D018441:Biofilms; D055113:Chronic Periodontitis / Q000382:microbiology*; D005881:Gingiva / Q000382:microbiology; D006801:Humans; D010514:Periodontal Pocket / Q000382:microbiology; D010641:Phenotype; D016966:Porphyromonas gingivalis / Q000302:isolation & purification* / Q000502:physiology; D012984:Software; D013045:Species Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods
chemical_list: D001426:Bacterial Proteins
keywords: Anaerobe; Chronic periodontitis; Mass spectrometry; Periodontal pocket; Porphyromonas gingivalis