Analysis of Black Fungal Biofilms Occurring at Domestic Water Taps (II): Potential Routes of Entry

Abstract

Formation of tenacious and massive black biofilms was occasionally observed at the water-air interphase of water taps and in associated habitats at several locations in Germany. Exophiala lecanii-corni was proven to be the dominant component of these biofilms. Water utility companies were interested to understand by which route fungi building these black biofilms enter their habitat at affected sites in domestic sanitary. A wide variety of fungi is known to be common in wet indoor environments, as well as in the drinking water resources. Two possible routes of entry are therefore considered as follows: (a) distribution by the drinking water system or (b) a retrograde route of colonisation. Previous compositional analysis revealed that the black constituents of biofilms primarily belong to the herpotrichiellaceous black yeast and relatives. Therefore, a systematic search for black fungi in the drinking water system was performed using Sabouraud's glucose agar medium with chloramphenicol and erythritol-chloramphenicol agar as isolation media. Cadophora malorum was the dominant fungus in the investigated drinking water systems, and samples taken from the house connections (n = 50; 74 %, <200 cfu/L), followed by a so far undescribed Alternaria sp. (28 %; <10 cfu/L) and E. castellanii (26 %; <10 cfu/L). Of note, C. malorum was not present in any previously analysed biofilm. Since E. lecanii-corni was not found in any water sample from the distribution system tested, but represented the most abundant species in dark biofilms previously analysed, a retrograde route of contamination in case of E. lecanii-corni can be assumed.

From Glacier to Sauna: RNA-Seq of the Human Pathogen Black Fungus Exophiala dermatitidis under Varying Temperature Conditions Exhibits Common and Novel Fungal Response

“…Examinations of bathwater and sludge in drainpipes that are warmed daily to over 42°C have identified several species of this medically important genus [20]. Recently, mass growth of dark fungal biofilms on water taps and associated habitats was observed in various German drinking water distribution systems [21,22]. Here, E .…”

Opportunistic Water-Borne Human Pathogenic Filamentous Fungi Unreported from Food

“…For instance, surface water sources harbor fungi that are mainly associated with plants and their debris, and causative agents of plant diseases, such as representatives from Botrytis and Cylindrocarpon [1,3]. Similarly, melanised fungi from Aureobasidium , Exophiala , and Rhinocladiella are mainly associated with groundwater [1,6]. Knowing the origin of waterborne opportunistic fungi is of a great importance for health risk assessments.…”

“…The presence of fungi in groundwater can thus affect the tap-water quality and this poses a health risk during tap-water-related activities [1,6,11,12] (Table 2). As reported by Novak Babič et al (2017), groundwater derived tap-water will more likely harbor species from Verticillium and different melanised fungi.…”

“…Yet, Exophiala (Herpotrichiellaceae) includes many water-related opportunistic pathogens, most of them classified under Biosafety Level 2 [8,15]. Recent literature reported on the presence of E. castellanii , E. dermatitidis , E. jeanselmei , E. oligosperma , E. phaeomuriformis and E. spinifera mainly from groundwater and groundwater derived tap-water, pointing towards groundwater as a possible source of these black fungi [6,12,16,17] (Table 2). Exophiala are associated with diverse spectra of opportunistic diseases such as otitis, keratitis, phaeohyphomycosis, and respiratory, cutaneous, and subcutaneous infections.…”

“…They are opportunistic pathogens, reported to cause endocarditis, keratitis, and peritonitis, respiratory, subcutaneous, and systemic infections [8]. Also close relatives of Exophiala , black filamentous fungi Rhinocladiella (Herpotrichiellaceae) were isolated from both groundwater and surface water, and they are one of the common contaminants of drinking water [6,12,17,26,33] (Table 2). They can cause chromoblastomycosis and cutaneous infections, particularly in tropical and sub-tropical regions [8].…”