Biotyping and virulence properties of skin isolates of Candida parapsilosis

Abstract

The biotype and virulence of skin isolates of Candida parapsilosis were compared with blood isolates of the same fungus. Morphotype, resistotype, and electrophoretic karyotype determinations did not reveal any special cluster with a unique or dominant pathogenic feature among all of the isolates, regardless of their source. However, all cutaneous isolates had uniformly elevated secretory aspartyl-protease (Sap) activity, more than four times higher than the enzyme activity of the blood isolates. They were also highly vaginopathic in a rat vaginitis model, being significantly more virulent than blood isolates in this infection model. In contrast, skin isolates were nonpathogenic in systemic infection of cyclophosphamide-immunodepressed mice, while some blood isolates were, in this model, highly pathogenic (median survival time, 2 days, with internal organ invasion at autopsy). Finally, skin isolates did not differ, as a whole, from blood isolates in their adherence to plastic. This property was associated with a morphotype, as defined by a colony with continuous fringe, which was present among both skin and blood isolates. While confirming the genetic heterogenicity of C. parapsilosis, our data strongly suggest that the potential of this fungus to cause mucosal disease is associated with Sap production and is substantially distinct from that of systemic invasion.

FIG. 1

Representative electrophoretic karyotype patterns of C. parapsilosis. Each numbered lane corresponds to a cluster of overlapping karyotypes, as defined in the text. Arrowed lanes at left and right are S. cerevisiae chromosomal markers, and their molecular size is expressed in megabases. For other details, see the text.

FIG. 2

Kinetics of vaginal infection by representative, high (■) and low (▴) Sap producer strains of C. parapsilosis isolated from the skin or blood, respectively, compared to a prototype C. albicans strain (5314 [○]) and its SAP2 gene null mutant (□). For experimental details, see the text and references to .