Candida tropicalis biofilms : artificial urine, urinary catheters and flow model

Adhesion to medical devices and biofilm formation are considered important virulence factors of Candida tropicalis. This work aimed to use artificial urine (AU) and urinary catheters, under flow conditions, for the study of C. tropicalis biofilms. Adhesion and biofilm formation on silicone and latex urinary catheters was quantified by crystal violet staining and colony forming units determination. Candida surface hydrophobicity was also evaluated, as well as the biofilms’ matrix content in terms of proteins and carbohydrates. Candida tropicalis was able to adhere and to form biofilms in the entire length of the catheters under flow conditions. It was verified that the isolate U69 adhered significantly more to both types of catheters,than the reference strain. However, biofilms formed by that isolate contained significantly less cultivable cells and higher biofilm biomass than biofilms of the reference strain. Detachment of cells from biofilms on latex catheter was lower compared to silicone catheter. The model with AU showed to be suitable for studies mimicking the real body conditions. Additionally, C. tropicalis was in fact able to colonize urinary catheters in the presence of AU and to detach from these catheters, showing their capacity to colonize distal sites.The authors acknowledge Cordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES), Brazil, for supporting Melyssa Negri work through grant BEX 4642/06-6. Moreover the authors would like to thank Fabio Luiz Grassi the design of Figure 1