Discrimination of Candida species by paper spray mass spectrometry

• Paper spray ionization allows species level Candida discrimination using lipid profiles.
• A bipolar experiment to acquire positive and negative ions from the same sample was implemented.
• Fusion of positive and negative mass spectra yielded species level discrimination.
• Eight closely related Candida species were characterized with a success rate of ca. 90%.

Ambient ionization mass spectrometry using paper spray is utilized for rapid discrimination of Candida species without sample preparation. The experiment is based on characteristic lipid profiles and is an extension to a procedure used for the discrimination of bacteria. Candida colonies were smeared onto filter paper pre-cut to a sharp tip, subsequently wetted with solvent and held at high potential. Charged droplets released by field emission were sucked into the mass spectrometer inlet and mass spectra were recorded. Eight closely related Candida species with clinical relevance and known phylogeny were investigated. Numerical data fusion of the positive and negative ion mass spectra and multivariate statistics (principal component analysis, followed by linear discriminant analysis) allowed species level discrimination with a prediction rate of ca. 90%.

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