Bioluminescence imaging increases in vivo screening efficiency for antifungal activity against device-associated Candida albicans biofilms

Fungal infections are a major problem for a growing number of mostly immunocompromised patients. Candida albicans is an important human fungal pathogen causing mucosal and deep tissue infections, of which the majority are associated with biofilm formation on medical implants. Animal models that are currently in use to test antifungal drugs are limited to ex vivo analyses, requiring host sacrifice that excludes longitudinal monitoring of dynamic processes during biofilm formation in the live host. As a solution, we introduce non-invasive, dynamic imaging and quantification of C. albicans biofilm formation in vivo and subsequent evaluation of treatment efficacy against these biofilms using bioluminescent C. albicans in a catheter-associated mouse model. Bioluminescence imaging (BLI) allowed us to evaluate baseline biofilm load before the start of therapy, which is necessary for correct evaluation and interpretation of antibiofilm efficacy in vivo. Moreover, we demonstrate that this BLI approach monitors the antibiofilm activity of different antifungal agents efficiently in vitro and in vivo. In this study, BLI revealed superior antibiofilm activity for echinocandins compared with amphotericin B and fluconazole. In vitro, anidulafungin showed the highest antibiofilm activity, followed by micafungin and caspofungin. In vivo, caspofungin significantly decreased the biofilm fungal load, as documented by the lower BLI signal and confirmed by CFU counts. In conclusion, this BLI approach increases the power and efficiency of screening and validation of antimycotics both under in vitro and in vivo conditions, thereby refining pre-clinical therapy studies.