Fungi of the genus Exophiala in tap water - potential etiological factors of phaeohyphomycoses

Introduction: Fungi arise interest owing to, among other things, a wide spectrum of potential pathogenicity. Migration of their spores with air, also through air-condition systems, has already been well documented in literature. In contrast, investigations addressing the role of drinking water supply systems in fungi transmission have, so far, been sparse and disputable. The vast majority of microfungi occurring in various types of waters are potential etiological factors of multiple surface and organ, and sometimes even systemic, mycoses. Their abundant proliferation in any aquatic environment always poses epidemiological risk. Aim of the study: The objective of the study was to characterize several species of the genus Exophiala isolated from tap water, with special attention paid to their potential pathogenicity. Material and methods: Water samples were collected following procedures adopted for bacteriological analyses. Mycological diagnostics was conducted according to the procedure elaborated by the authors. The study was carried out since November 2008 till March 2009. Water samples were collected once a month from 10 terminal points “at the clients”. Results: In total, 48 liters of tap water were analyzed. Out of the numerous group of yeast-like and mould fungi, fungi forming dark-brown colonies were observed, commonly referred to as “black yeast”. Their count reached nearly 690 colonies. The study enabled identification of three Ascomycota species of the genus Exophiala (family: Herpotrichiellaceae): E. castellani, E. jeanselmei and E. spinifera. In safety classification they belong to BSL-2 class, i.e. to potential pathogens. They are etiological factors of phaeohyphomycoses, and subcutaneous infections in particular. Conclusions: The conducted study proved that drinking water may also constitute one of the significant reservoirs of fungi potentially pathogenic to humans.