Evaluation of Virulence in Various Candida Species: In Vitro and In Vivo Study

Objective: In vitro virulence features of Candida strains isolated from blood specimens of 85 non-neutropenic patients, and in vivo (murine) tissue invasions were assessed in this study. Material and Methods: Virulence tests were examined at a single strain (85 isolates) of the patients. Surface hydrophobicity, attachment to epithelial cells, phospholipase and proteinase enzyme activity were examined in vitro virulence factors. Strains diluted with PBS were inoculated through the tail veins of the mice (Swiss albino). Results: In vitro virulence of the persisting strains was not higher than the ones which were isolated only once. Phospholipase activity was only detected in C.albicans strains and 87.5% of the C.albicans strains showed tissue invasion. The only strain that did not demonstrate tissue invasion was the one which showed no in vitro enzyme activity. In vitro virulence of the other species which do not produce phospholipase were lower than C.albicans. The species with the lowest virulence was found to be C.krusei. Significant correlation between tissue invasion and enzyme secretion (phospholipase and/or proteinase) suggests that enzyme secretion was more important than adhesive property for invasion. However, the absence of invasion in C.parapsilosis strains with high proteinase secretion was an interesting finding. Conclusion: It was highlighted in this study that the identification of the clinical isolates at the species level is really important as Candida species had different in vivo and in vitro virulence factors.