Session: Poster Session: Fungal Biofilms
Sunday, October 26, 2008: 12:00 AM
Room: Hall C
Background: Candida biofilms are mainly studied in various in vitro systems but these models do not reflect the influence of the host immune system and the infection site. We developed a new, simple in vivo Candida biofilm model and studied the role of Bcr1 transcription factor, which was previously shown to play an important role in biofilm regulation. Adhesin Als3 is under control of Bcr1. Methods: Up to 10 polyurethane intravenous catheter segments, inoculated with Candida, were implanted under the skin of specific pathogen free, dexamethasone immunosuppressed, Sprague Dawley rats. The biofilms were characterised by fluorescence microscopy, scanning electron microscopy and colony counting. Results were compared with in vitro grown biofilms. Candida albicans strain SC5314, parental strain BWP17 and the als3/als3 and bcr1/bcr1 mutant strains were used for the experiments. Results: In vivo biofilm development was slower than in vitro and the maximum increase in Candida cells was lower (10 fold increase compared to 100 fold increase after 48 hours). Mature biofilms were obtained after two days. bcr1/bcr1 formed biofilms in our in vivo model which contrasts to results obtained in an in vivo central venous catheter model (Nobile et al., 2006). Also the als3/als3 mutant was unaffected in biofilm formation in vivo. Contamination was excluded by RT-PCR (no ALS3 mRNA and no BCR1 mRNA was detected in their respective mutant strains). Biofilm growth by bcr1/bcr1 and als3/als3 was also unaffected in vitro using RPMI medium but no biofilm was formed in Spider medium, confirming previous results. Conclusions: We have developed a simple in vivo Candida biofilm model. Bcr1 transcription factor does not seem to be essential for biofilm formation in this model. Environmental conditions seem to have an important influence on biofilm formation. Experiments studying the activity of antifungal agents in our in vivo model will be started up.