Urinary Tract Infections: Fungi (Candida spp.)

Urinary tract infections (UTIs) are among the most common microbial infections in humans. Although most cases of infection are of bacterial etiology, fungal-related UTIs are increasing, with Candida spp. dominating this group of eukaryotic pathogens. Among the Candida spp., Candida albicans remains the most important and frequently isolated species, however, other non-albicans Candida species (NACS) are emerging as important contributors to fungal UTIs. The presence of Candida spp. in the urine (candiduria) does not necessarily indicate a UTI, and may represent contamination as a component of the resident microflora, or even initial stages of a developing systemic infection, and thus, several parameters need to be carefully considered together with available clinical information regarding the patient before initiating antifungal treatment. In this review, we present an overview of urinary tract infections with fungal pathogens as the primary etiologic agent. Due to their significant clinical relevance we focus on infections caused by Candida spp., in particular, C. albicans as the most important representative and prototypical fungal pathogen. We discuss basic cell biology, pathogenicity mechanisms, epidemiology, clinical diagnosis, and treatment options. We also highlight certain aspects of host response, particularly the role of the immunological response initiated as a consequence of tissue colonization and during infection.