Abstract

In the present study, we determined the in vitro and in vivo virulence characteristics ofCandida isolates from 75 non-neutropenic patients with candidemia and analyzed the isolates by receiver-operating characteristics (ROC) analysis to define threshold values of adhesion and hydrophobicity occurring in invasive Candida isolates. Specific virulence traits that were measured included hydrophobicity, epithelial cell adhesion, phospholipase and proteinase activity. In our in vivo investigations, all isolates were diluted in phosphate-buffered saline (PBS) and were administered to mice (Swiss albino) through tail-vein injection. Liver and spleen tissues were evaluated for evidence of invasion. Though onlyCandida albicans isolates produced detectable phospholipase activity, all isolates secreted proteinase enzyme. However, while this observation was significant among C. albicans and Candida parapsilosis isolates, the reverse was seen for Candida tropicalisand Candida krusei isolates. Interestingly, in contrast with C. parapsilosis and C. tropicalis, lower median adhesion values were determined for C. albicans and C. krusei, particularly in isolates that showed invasion in mouse experiments. It has not been possible to identify meaningful threshold values for adhesion and hydrophobicity in the repeated ROC analysis on the sub-groups in differentiating the isolates that cause and do not cause invasion in mice among the various Candida isolates.

Key words: Candidemia, virulence factors, ROC analysis