Development and Characterization of an In Vivo Central Venous Catheter Candida albicans Biofilm Model

Abstract

Biofilms represent a niche for microorganisms where they are protected from both the host immune system and antimicrobial therapies. Biofilm growth serves as an increasing source of clinical infections. Candida infections are difficult to manage due to their persistent nature and associated drug resistance. Observations made in biofilm research have generally been limited to in vitro models. Using a rat central venous catheter model, we characterized in vivo Candida albicans biofilm development. Time-course quantitative culture demonstrated a progressive increase in the burden of viable cells for the first 24 h of development. Fluorescence and scanning electron microscopy revealed a bilayered architecture. Adjacent to the catheter surface, yeast cells were densely embedded in an extracellular matrix. The layer adjacent to the catheter lumen was less dense. The outermost surface of the biofilm contained both yeast and hyphal forms, and the extracellular material in which they were embedded appeared fibrous. These architectural features were similar in many respects to those described for in vitro models. However, scanning electron microscopy also revealed host cells embedded within the biofilm matrix. Drug susceptibility was determined by using two assays and demonstrated a biofilm-associated drug resistance phenotype. The first assay demonstrated continued growth of cells in the presence of supra-MIC antifungal drug concentrations. The second assay demonstrated reduced susceptibility of biofilm-grown cells following removal from the biofilm structure. Lastly, the model provided sufficient nucleic material for study of differential gene expression associated with in vivo biofilm growth. Two fluconazole efflux pumps, CDR1 and CDR2, were upregulated in the in vivo biofilm-associated cells. Most importantly, the studies described provide a model for further investigation into the molecular mechanisms of C. albicans biofilm biology and drug resistance. In addition, the model provides a means to study novel drug therapies and device technologies targeted to the control of biofilm-associated infections.

Plasticity of Candida albicans Biofilms

“…However, there are several models, including those incorporating flow and those performed in an in vivo setting, that are markedly different. Andes and coworkers (192) and Ghannoum and coworkers (191) developed in vivo intravenous catheter models, and Andes and coworkers (187) developed an in vivo urinary catheter model. In the original intravenous model developed by Andes et al (31,192) (Fig.…”

“…Andes and coworkers (192) and Ghannoum and coworkers (191) developed in vivo intravenous catheter models, and Andes and coworkers (187) developed an in vivo urinary catheter model. In the original intravenous model developed by Andes et al (31,192) (Fig. 5A), a polyethylene tube was inserted into the jugular vein of a rat, conditioned by back flow (without the addition of C. albicans for 24 h), and flushed.…”

Temporal analysis of Candida albicans gene expression during biofilm development

“…Antifungal drug therapy is used to treat denture stomatitis, but infection often re-establishes soon after completion of treatment (MacEntee, 1985). Biofilm formation on the surface of intravenous catheters promotes systemic candidiasis because the biofilm serves as the source of fungal cells that can seed the bloodstream (Andes et al, 2004). Mortality of patients with systemic candidiasis can be as high as 40 % (Edmond et al, 1999;Gudlaugsson et al, 2003;Wey et al, 1988).…”

A rabbit model for evaluation of catheter-associated fungal biofilms

“…Fluorescence and scanning electron microscopy revealed a bilayered architecture. 9 Quantification of in vivo catheter biofilms is commonly performed using QCC method. In our studies, we optimized and used the QCC assay to quantify biofilms formed on catheters in vivo.…”

“…Andes et al used SEM and confocal scanning laser microscopy to reveal a bilayered architecture of CVC-associated in vivo biofilms. 9 In our study, we used SEM to observe biofilms formed on catheters in vivo. Susceptibility of Candida biofilms formed on catheters in vivo to locked antimicrobial agents is most commonly determined by assessing cell viability as measured by CFUs.…”