Candida tropicalis biofilms: effect on urinary epithelial cells.

Candida tropicalis infection is strongly associated with the presence of biofilms in urinary catheters. Thus, the aim of this work was to study the behaviour of C. tropicalis in biofilms of different ages (24-120 h) formed in artificial urine (AU) and their effect in human urinary bladder cells (TCC-SUP). Reference strain ATCC 750 and two isolates from patients with candiduria (U69 and U75) were used in this study. The adhesion to human cells was evaluated after 2 h of contact with Candida biofilms, using the Crystal violet staining method, and the human cells response was evaluated in terms of activity inhibition and cell damage. Candida tropicalis aspartyl proteinase (SAPT) gene expression was determined by real-time PCR. Candida tropicalis biofilm cells were able to adhere to TCC-SUP cells. The highest extent of yeast attachment was obtained for the 72 h old biofilm cells. Yeasts affected TCC-SUP cells, with 120 h-biofilm cells causing the highest levels of cell injury. Generally, SAPT3 was highly expressed and SAPT4 was only detected in the reference strain. Overall, it is important to highlight that C. tropicalis cells detached from biofilms are able to colonize human cells and cause some injury and reduction of metabolic activity.