Phenotypic identification of Porphyromonas gingivalis validated with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Thomas E Rams; Jacqueline D Sautter; Adam Getreu; Arie J van Winkelhoff

doi:10.1016/j.micpath.2016.01.021

Phenotypic identification of Porphyromonas gingivalis validated with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Microb Pathog. 2016 May:94:112-6. doi: 10.1016/j.micpath.2016.01.021. Epub 2016 Feb 4.

Authors

Thomas E Rams¹, Jacqueline D Sautter², Adam Getreu², Arie J van Winkelhoff³

Affiliations

¹ 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.
² Department of Periodontology and Oral Implantology, Oral Microbiology Testing Service Laboratory, Temple University School of Dentistry, Philadelphia, PA, 19140, USA.
³ Department of Medical Microbiology, and Center for Dentistry and Oral Hygiene, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.

PMID: 26835658
DOI: 10.1016/j.micpath.2016.01.021

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.

Keywords: Anaerobe; Chronic periodontitis; Mass spectrometry; Periodontal pocket; Porphyromonas gingivalis.

MeSH terms

Adult
Bacterial Proteins / analysis
Bacterial Proteins / isolation & purification
Bacteroidaceae Infections / microbiology*
Biofilms
Chronic Periodontitis / microbiology*
Gingiva / microbiology
Humans
Periodontal Pocket / microbiology
Phenotype
Porphyromonas gingivalis / isolation & purification*
Porphyromonas gingivalis / physiology
Software
Species Specificity
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / instrumentation
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods

Substances

Bacterial Proteins