Bioluminescence Imaging to Study Mature Biofilm Formation by Candida spp. and Antifungal Activity In Vitro and In Vivo

The widespread use of indwelling medical devices has increased the number of device-related infections in hospitalized patients. These infections are often associated with the formation of biofilms on the medical implants that are difficult to treat because of their resistance to the classical antifungal drugs. The most common fungi isolated from catheters and other medical devices are Candida species. The Candida genus contains multiple species of which C. albicans and C. glabrata are the two most common pathogenic yeasts in humans. A limited number of animal models is available for investigating host-pathogen interactions and testing novel antifungal drugs in vivo against these species. Fungal load in biofilms in these models is traditionally analyzed postmortem, requiring host sacrifice and enumeration of microorganisms from individual biofilms in order to evaluate the amount of colony forming units and the efficacy of antifungal treatment. Bioluminescence imaging (BLI) made compatible with small animal models for in vivo biofilm formation is a valuable tool to follow biofilm development and its treatment longitudinally. Due to the noninvasive nature of BLI, the imaging procedure can be repeated in the same animal, allowing for follow-up of the biofilm growth in vivo without removing the implanted device or detaching the biofilm from its substrate. Although detecting a quantifiable in vivo BLI signal from biofilms formed on the inside of implanted catheters is challenging, BLI proved to be a practical tool in the study of fungal biofilms. This method describes the use of BLI for in vitro and in vivo follow-up of device-related fungal biofilm formation in mice and rats and antifungal activity testing against both C. albicans and C. glabrata device-associated biofilms. It can further be applied for efficient in vivo screening for interesting genes of the pathogen and the host involved in biofilm formation.status: publishe