Abstract
Urinary tract infections (UTIs) are quite common and mainly caused by bacteria such as Escherichia coli. However, when patients have urinary catheters, fungal infections comprise up to 15% of these types of infections. Moreover, fungal UTIs have a high mortality, due to rapid spreading of the fungi to the kidneys. Most fungal UTIs are caused by Candida species, among which Candida albicans and Candida glabrata are the most common. C. glabrata is an opportunistic pathogenic yeast, phylogenetically quite close to Saccharomyces cerevisiae. Even though it is commonly isolated from the urinary tract and rapidly acquires resistance to antifungals, its pathogenesis has not been studied extensively in vivo. In vivo studies require high numbers of animals, which can be overcome by the use of non-invasive imaging tools. One such tool, bioluminescence imaging, has been used successfully to study different types of C. albicans infections. For C. glabrata, only biofilms on subcutaneously implanted catheters have been imaged using this tool. In this work, we investigated the progression of C. glabrata UTIs from the bladder to the kidneys and the spleen. Furthermore, we optimized expression of a red-shifted firefly luciferase in C. glabrata for in vivo use. We propose the first animal model using bioluminescence imaging to visualize C. glabrata in mouse tissues. Additionally, this UTI model can be used to monitor antifungal activity in vivo over time.
Highlights
Candida species are the most common causative agents of opportunistic, nosocomial, fungal infections [1]
Since the use of bioluminescence imaging (BLI) can strongly reduce the number of animals needed for in vivo studies, we investigated how we could reach the highest possible luciferase expression in C. glabrata
We investigated the progression of C. glabrata urinary tract infections in mice
Summary
Candida species are the most common causative agents of opportunistic, nosocomial, fungal infections [1]. A luciferase gene needs to be stably expressed in the fungus, which can convert a substrate into light [16] Both the Gaussia princeps (copepod) and Photinus pyralis (firefly) luciferases have been used successfully in C. albicans to image invasive, oral, cutaneous, vaginal, and implant-related biofilm infections [17,18,19,20,21]. A red-shifted firefly luciferase was genetically engineered to have an emission peak at 625 nm, further improving deep-tissue imaging [17] Both these luciferases could be used to image the reduced fungal burden following antifungal treatment for both invasive and implant-related biofilm infections [17,23]. In order to reduce the number of animals needed and to make temporal studies possible, we developed a model in which we imaged bladder colonization using bioluminescence, which can be used to determine the effectiveness of antifungal treatment
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