Indoor wet cells as a habitat for melanized fungi, opportunistic pathogens on humans and other vertebrates

Abstract

Indoor wet cells serve as an environmental reservoir for a wide diversity of melanized fungi. A total of 313 melanized fungi were isolated at five locations in Guangzhou, China. Internal transcribed spacer (rDNA ITS) sequencing showed a preponderance of 27 species belonging to 10 genera; 64.22% (n = 201) were known as human opportunists in the orders Chaetothyriales and Venturiales, potentially causing cutaneous and sometimes deep infections. Knufia epidermidis was the most frequently encountered species in bathrooms (n = 26), while in kitchens Ochroconis musae (n = 14), Phialophora oxyspora (n = 12) and P. europaea (n = 10) were prevalent. Since the majority of species isolated are common agents of cutaneous infections and are rarely encountered in the natural environment, it is hypothesized that indoor facilities explain the previously enigmatic sources of infection by these organisms.

Microorganisms populating the water-related indoor biome

“…Similarly to bacteria, fungi colonising bathroom surfaces can also originate from tap water or skin. Water-borne fungi represent a diversity of species from the genera (Table 1) (Wang et al 2018;Novak Babič et al 2017a, b;Moat et al 2016). These genera can be isolated from taps, sinks and seals between ceramic bathroom tiles ( Fig.…”

Opportunistic Water-Borne Human Pathogenic Filamentous Fungi Unreported from Food

“…They have been linked to humid indoor niches, swimming facilities, but also to plant and human diseases. They mainly cause surface infections of skin and nails [14,15] (Table 2). Yet, Exophiala (Herpotrichiellaceae) includes many water-related opportunistic pathogens, most of them classified under Biosafety Level 2 [8,15].…”

“…They mainly cause surface infections of skin and nails [14,15] (Table 2). 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).…”

“…However, modern society uses substantial amounts of tap-water for showering, bathing, cooking, and cleaning [1,54]; most frequently performed with household appliances, such as washing machines and dishwashers. They represent novel niches for propagation of waterborne fungi, particularly polyextremotolerant species Exophiala dermatitidis and E. phaeomuriformis , and these should be taken into consideration for risk assessment linked to fungal diseases [15,17,55]. Together with the above-mentioned fungi, Phialophora (Herpotrichiellaceae) and Ochroconis (Sympoventuriaceae) were recently linked to nutrient-poor tap-water [30,31] and indoor wet niches, such as bathrooms and washing machines [15,55].…”

“…They represent novel niches for propagation of waterborne fungi, particularly polyextremotolerant species Exophiala dermatitidis and E. phaeomuriformis , and these should be taken into consideration for risk assessment linked to fungal diseases [15,17,55]. Together with the above-mentioned fungi, Phialophora (Herpotrichiellaceae) and Ochroconis (Sympoventuriaceae) were recently linked to nutrient-poor tap-water [30,31] and indoor wet niches, such as bathrooms and washing machines [15,55]. Some species within Phialophora and Ochroconis were reported as causative agents of cutaneous and subcutaneous infections (Table 2) [8].…”