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. 2018 Nov;30(6):813-820.
doi: 10.1177/1040638718805537. Epub 2018 Oct 3.

Rapid differentiation of Staphylococcus aureus subspecies based on MALDI-TOF MS profiles

Marta Pérez-Sancho  1   2 , Ana I Vela  1   2 , Pilar Horcajo  1   2 , María Ugarte-Ruiz  1   2 , Lucas Domínguez  1   2 , José F Fernández-Garayzábal  1   2 , Ricardo de la Fuente  1   2
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Rapid differentiation of Staphylococcus aureus subspecies based on MALDI-TOF MS profiles

Marta Pérez-Sancho et al. J Vet Diagn Invest. 2018 Nov.

Abstract

Staphylococcus aureus encompasses 2 subspecies ( aureus and anaerobius) with significant differences in their epidemiology and pathogenicity. We evaluated the suitability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the rapid identification of both subspecies using a panel of 52 S. aureus isolates (30 subsp. anaerobius and 22 subsp. aureus) recovered from different origins, countries, and years. The on-board library identification system correctly identified 42 of 52 (81%) S. aureus isolates at the species level with score values >2.0. Limited performance was observed for differentiation of S. aureus subspecies (particularly subsp. anaerobius). Visual inspection of MALDI-TOF MS profiles identified 5 subspecies-specific mass peaks ( m/ z 3430 and 6861 in S. aureus subsp. anaerobius, and m/ z 4046, 6890, and 8093 in S. aureus subsp. aureus) with 100% sensitivity and specificity values, which is potentially useful for differentiating these subspecies. The suitability of 3 models, Genetic Analysis (GA), Quick Classifier (QC), and Supervised Neural Network, for automatic identification of both subspecies was evaluated using the Recognition Capability (RC) and Cross Validation (CV) values provided by the on-board ClinProTools software. The GA and QC models reached RC and CV values of 100%. Both models were externally validated using a panel of 26 S. aureus isolates of both subspecies, with both models correctly classifying all isolates of both subspecies. MALDI-TOF MS coupled with ClinProTools software represents a rapid and simple approach for S. aureus subspecies discrimination.

Keywords: MALDI-TOF MS; Staphylococcus aureus subspecies.

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Conflict of interest statement

Declaration of conflicting interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
ClinProTools illustrations: A. gel view representation obtained from the mass spectra of Staphylococcus aureus subsp. aureus (1, upper diagram, 20 isolates) and S. aureus subsp. anaerobius (2, lower diagram, 30 isolates) showing in the x-axis the 5 mass peaks m/z 3430, 4046, 6861, 6890, and 8093 proposed for S. aureus subspecies differentiation; B. 2-dimensional peak distribution diagram (isolate distribution map) of S. aureus subsp. aureus (triangles) and S. aureus subsp. anaerobius (open circles) isolates.
See this image and copyright information in PMC

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