Hemolytic factor production by clinical isolates of Candida species.

Most cases of fungal bloodstream infections (BIs) are attributed to Candida albicans; however, non-Candida albicans Candida species have recently been identified as common pathogens. Although hemolytic factor is known to be putative virulence factor contributing to pathogenicity in Candida species, its production is poorly evaluated. The present study was undertaken to analyze the production of hemolytic factor by C. albicans (10), C. tropicalis (13), and C. parapsilosis (8) isolates associated with BIs. Data of hemolysis zones on plate assay revealed that the majority of C. albicans isolates produced mild hemolytic activity whereas the majority of C. tropicalis produced strong activity. None of the tested C. parapsilosis isolates exhibited hemolysis on plate assay. We also evaluated the hemolytic activity in the cell-free broth. There were no significant differences (P > 0.05) in the secreted hemolytic activity among intra-species isolates. Different levels of secreted hemolytic factor were observed for Candida species, where C. tropicalis exhibited the highest production of hemolytic factor (P < 0.05) followed by C. albicans and C. parapsilosis. Inhibition of hemolysis (up to 89.12 %) from culture supernatant, following incubation with the lectin Concanavalin A (Con A), was observed for all three Candida species. This finding suggests that the secreted hemolytic factor of C. tropicalis and C. parapsilosis may be a mannoprotein, similar to that described for C. albicans.