Congress of the International Society for Human and Animal Mycology (ISHAM) edition:17th location:Tokyo, Japan date:May 25-29th 2009
More than half of all human microbial infections can be associated to biofilms, highlighting the impact of biofilm on public health. Candida albicans can form biofilms on a wide variety of medical devices such as urinary and vascular catheters, but also dental, joint and voice prostheses, pacemakers, ocular lenses. We have optimized an in vivo biofilm model for Candida based on a subcutaneous rat model previously described by Van Wijngaerden et al. (1999). Pieces of three-lumen catheters treated with serum are implanted under the skin of rat after an adhesion phase with Candida cells. Biofilms, assessed by colony forming units and scanning electron microscopy, reach an optimal size after two days, but they can remain in the host for up to 9 days. Immunosuppression treatment of the animal host increases the reproducibility of the biofilm generated inside the lumens. A critical step in biofilm production is the adhesion phase: incubating cells in RPMI medium instead of Spider or YNB glucose resulted in an increased biofilm formation, not only in wild type but also in strains defectuous in biofilm development in other models, such as als3. Both wild type and als3 can form biofilm in vitro on 96-well plate polystyrene substrate and on polyurethane disk when grown in RPMI, but the mutant does not when grown in Spider. We also observed biofilm formation in vivo with als3, this mutant being able to adhere and grow as hyphae in RPMI. In contrast, cells of the cph1 efg1 strain are not able to form biofilm in in vitro assays in RPMI, and also do not generate biofilm in vivo. Even in absence of constant flow, adherence is crucial to the in vivo subcutaneous biofilm model.