Rapid Differentiation of Closely Related Candida Species and Strains by Pyrolysis-Mass Spectrometry and Fourier Transform-Infrared Spectroscopy

Abstract

Two rapid spectroscopic approaches for whole-organism fingerprinting of pyrolysis-mass spectrometry (PyMS) and Fourier transform-infrared spectroscopy (FT-IR) were used to analyze a group of 29 clinical and reference Candida isolates. These strains had been identified by conventional means as belonging to one of the three species Candida albicans, C. dubliniensis(previously reported as atypical C. albicans), and C. stellatoidea (which is also closely related to C. albicans). To observe the relationships of the 29 isolates as judged by PyMS and FT-IR, the spectral data were clustered by discriminant analysis. On visual inspection of the cluster analyses from both methods, three distinct clusters, which were discrete for each of the Candida species, could be seen. Moreover, these phenetic classifications were found to be very similar to those obtained by genotypic studies which examined the HinfI restriction enzyme digestion patterns of genomic DNA and by use of the 27A C. albicans-specific probe. Both spectroscopic techniques are rapid (typically, 2 min for PyMS and 10 s for FT-IR) and were shown to be capable of successfully discriminating between closely related isolates of C. albicans, C. dubliniensis, and C. stellatoidea. We believe that these whole-organism fingerprinting methods could provide opportunities for automation in clinical microbial laboratories, improving turnaround times and the use of resources.

Using metabolic fingerprinting of plants for evaluating nitrogen deposition impacts on the landscape level

“…This 'holistic' approach allows highthroughput, unbiased examination of sample biochemistry and, through suitable interpretation, can be used to monitor plant responses to abiotic or biotic influences (Goodacre et al, 1998). Previous work on food quality (Lai et al, 1994;Goodacre & Anklam, 2001;Ellis et al, 2002), bacterial and fungal species (Helm et al, 1991;Goodacre et al, 1998;Timmins et al, 1998), and plant systems (Gidman et al, 2003;Johnson et al, 2003), including those subjected to N application (Gidman et al, 2004(Gidman et al, , 2005, has already indicated the potential of this approach.…”

Candida albicans or Candida dubliniensis?

“…62 Whole organism fingerprinting Recent developments in analytical instruments have made the rapid, automated and accurate identification of clinical yeast possible without the need for extensive sample preparation. 66 Physiochemical spectroscopic methods such as pyrolysis-mass spectrometry, Fourier transform-infrared spectroscopy and UV resonance Raman spectroscopy allows for the direct analyses of samples and provides so called whole organism fingerprints which is a phenotypic measure of the physiochemical composition of the organism. It must, however, be noted that other sources of chemical variation in biological samples, such as media composition and colony size should be minimised to obtain standardised spectra for each organism.…”

“…67 Pyrolysis-mass spectrometry has been used successfully in the identification of clinically relevant bacteria and involves the thermal degradation of the sample and the production of volatile molecular fragments. 66 These fragments are analysed using a mass-spectrometer, yielding a mass spectrum which measures the strengths of covalent bonds between the molecules of the organism. It was found that the mass spectra of C. dubliniensis and C. albicans showed little qualitative differences, but quantitative differences between the spectra could be observed.…”

“…Fourier transform-infrared (FT-IR) spectroscopy measures vibrations of functional groups and polar bonds. 66 It has been reported that the complex biochemical fingerprints obtained using this technique can be used to identify bacteria and fungi at strain level. When the FT-IR spectra of C. albicans and C. dubliniensis were compared, no qualitative differences were again observed.…”

Characterisation of intact microorganisms using electrospray ionisation mass spectrometry

“…1 and 2 respectively. The cluster analysis process is based on that developed by Gutteridge et al [12] to analysis PyMS data, and has been adapted in-house for the analyses of high dimensional infrared [13] and Raman spectra [14]. Brie£y, the initial stage involved the reduction of the dimensionality of the ESI-MS data by principal components analysis (PCA) [15].…”