Candida albicans biofilm formation in a new in vivo rat model

Abstract

Device-associated microbial growth, including Candida biofilms, represents more than half of all human microbial infections and, despite a relatively small risk of implant-associated diseases, this type of infection usually leads to high morbidity, increased health-care costs and prolonged antimicrobial therapy. Animal models are needed to elucidate the complex host-pathogen interactions that occur during the development of attached and structured biofilm populations. We describe here a new in vivo model to study Candida biofilm, based on the avascular implantation of small catheters in rats. Polyurethane biomaterials challenged with Candida cells were placed underneath the skin of immunosuppressed animals following only minor surgery. The model allowed the study of up to ten biofilms at once, and the recovery of mature biofilms from 2 days after implantation. The adhering inoculum was adjusted to the standard threshold of positive diagnosis of fungal infection in materials recovered from patients. Wild-type biofilms were mainly formed of hyphal cells, and they were unevenly distributed across the catheter length as observed in infected materials in clinical cases. The hyphal multilayered structure of the biofilms of wild-type strains was observed by confocal microscopy and compared to the monolayer of yeast or hyphal cells of two well-known biofilm-deficient strains, efg1D/efg1D cph1D/cph1D and bcr1D/ bcr1D, respectively. The subcutaneous Candida biofilm model relies on the use of implanted catheters with accessible, fast and minor surgery to the animals. This model can be used to characterize the ability of antimicrobial agents to eliminate biofilms, and to evaluate the prophylactic effect of antifungal drugs and biomaterial coatings.

Transcription factor Efg1 contributes to the tolerance of Candida albicans biofilms against antifungal agents in vitro and in vivo

“…To this end, we determined the miconazole sensitivity of biofilms of C. albicans mutants affected in cyclic AMP signalling, as it was previously reported that the cAMP signalling pathway is involved in the tolerance of planktonic C. albicans cells to miconazole (Jain et al, 2003). In addition, we validated the obtained in vitro data in an in vivo biofilm model, in which we administered miconazole intraperitoneally to rats (Ricicová et al, 2010). We finally demonstrated that by using miconazole as a model antimycotic compound, which is mainly used to treat topical fungal infections (Kyle & Dahl, 2004), these findings can be translated to other antimycotics such as amphotericin B (AmB) and caspofungin (CAS), which are used specifically in combatting systemic fungal infections (Kuhn et al, 2002a).…”

“…Control solution without miconazole was also prepared. In vivo biofilm drug susceptibility assays were determined using 1 cm pieces of serumcoated triple-lumen polyurethane catheters (Arrow International) as described previously (Ricicová et al, 2010). Briefly, animals were immunosuppressed 24 h prior to catheter implantation and throughout the whole experimental procedure (up to 9 days).…”

“…To assess the increased sensitivity of sessile cells of the Defg1 mutant to miconazole under in vivo conditions, we used the recently developed subcutaneous biofilm rat model, in which biofilm growth on catheter fragments inoculated with the different C. albicans strains prior to implantation was determined (Ricicová et al, 2010). The numbers of sessile C. albicans cells recovered from the implanted catheters in vivo are given in Fig.…”

Role of cell surface hydrophobicity in Candida albicans biofilm

“…The expression data from planktonic culture or 24 h dispersal cells were used as reference samples to determine ΔΔ Ct values. The primers for ACT1 and were previously described by Řičicová et al [13]. The primers for CSH1 were designed by Dr.…”

Candida Biofilms on Oral Biomaterials

“…The rat catheter biofilm infection model (Andes et al, 2004;Lazzell et al, 2009;Ricicová et al, 2010) allows evaluation in vivo of the comportment of one microorganism that is exposed to host proteins and immune factors. Other animal models have been utilized to monitor materials and devices that are placed in the bathing conditions of the oral cavity and to mimic denture stomatitis with fungal invasion and neutrophil infiltration of the adjacent mucosa.…”