Looking into the virulence of Candida parapsilosis

Editorial In many diagnostic microbiology laboratories the species identification process starting from cultured colonies has recently undergone some significant changes. Where not long ago car-bon/nitrogen source utilization tests in the form of colorful tubes or well-based devices down to chip card size dominated the field, we now find a purely biophysical instrument, a MALDI-ToF mass spectrometer. Instead of evaluating growth only after overnight incubation, the results are now available within minutes of sample processing. 1 At the same time, the depth of differentiation is significantly increased beyond what a cultural method can do. In an assimilation assay the number of data points is limited by the number of compounds tested, in mass spectrometry by the number of biomarker ions observed. In the first, common numbers range between 16 and 42, many of these not being able to discriminate between closely related species. In the latter, the number of biomarker ions observed usually exceeds 100, depending on spectrum quality. These are spread out over a mass range of approximately 10 kDa and most of them are unique even between closely related species, to some degree even between different isolates of the same species. It is not surprising that this new availability to easily type with this depth has led to increased observation of " rare " microorganisms in clinical specimen. This is not only true for bacteria , but also for fungi. Mainly four complexes of species occur in clinical specimen, that are now easily distinguished: (1) Candida albicans/dubliniensis, 2 (2) C. glabrata/nivariensis/bracarensis, 3,4 (3) C. parapsilosis/orthopsilosis/metapsilosis, 3,5 and (4) what was identified as C. famata (Debaryomyces hansenii) by biochemical assays is obviously more likely to be a strain of C. palmioleophila or C. guilliermondii. Here the clinical microbiologist is currently faced with a dilemma. What do we tell a clinician to do about C. pal-mioleophila unless it came from a sterile site? Do we actually report " C. metapsilosis " or just a " C. parapsilosis group " isolate? Clearly, the answer to these questions warrants investigation of the pathogenic potential of these—as compared with the major pathogenic yeast C. albicans—less frequent species. One of the traits shared by pathogenic Candida species, in contrast to their closely related apathogenic sibling species, is the assembly of large gene families which constitute potential virulence factors. 8 Among these, probably the most prominent is the family of ten secretory aspartic proteases of C. …