The Black Yeast Exophiala dermatitidis and Other Selected Opportunistic Human Fungal Pathogens Spread from Dishwashers to Kitchens

Abstract

We investigated the diversity and distribution of fungi in nine different sites inside 30 residential dishwashers. In total, 503 fungal strains were isolated, which belong to 10 genera and 84 species. Irrespective of the sampled site, 83% of the dishwashers were positive for fungi. The most frequent opportunistic pathogenic species were Exophiala dermatitidis, Candida parapsilosis sensu stricto, Exophiala phaeomuriformis, Fusarium dimerum, and the Saprochaete/Magnusiomyces clade. The black yeast E. dermatitidis was detected in 47% of the dishwashers, primarily at the dishwasher rubber seals, at up to 106 CFU/cm2; the other fungi detected were in the range of 102 to 105 CFU/cm2. The other most heavily contaminated dishwasher sites were side nozzles, doors and drains. Only F. dimerum was isolated from washed dishes, while dishwasher waste water contained E. dermatitidis, Exophiala oligosperma and Sarocladium killiense. Plumbing systems supplying water to household appliances represent the most probable route for contamination of dishwashers, as the fungi that represented the core dishwasher mycobiota were also detected in the tap water. Hot aerosols from dishwashers contained the human opportunistic yeast C. parapsilosis, Rhodotorula mucilaginosa and E. dermatitidis (as well as common air-borne genera such as Aspergillus, Penicillium, Trichoderma and Cladosporium). Comparison of fungal contamination of kitchens without and with dishwashers revealed that virtually all were contaminated with fungi. In both cases, the most contaminated sites were the kitchen drain and the dish drying rack. The most important difference was higher prevalence of black yeasts (E. dermatitidis in particular) in kitchens with dishwashers. In kitchens without dishwashers, C. parapsilosis strongly prevailed with negligible occurrence of E. dermatitidis. F. dimerum was isolated only from kitchens with dishwashers, while Saprochaete/Magnusiomyces isolates were only found within dishwashers. We conclude that dishwashers represent a reservoir of enriched opportunistic pathogenic species that can spread from the dishwasher into the indoor biome.

Fungal Contaminants in Drinking Water Regulation? A Tale of Ecology, Exposure, Purification and Clinical Relevance

“…People may come across them on a daily basis at different exposure points; directly while using water for drinking, bathing and showering, or indirectly due to the use of appliances connected to the water supply, for instance dishwashers and washing machines (Figure 1) [19,27,67,80]. …”

Opportunistic Water-Borne Human Pathogenic Filamentous Fungi Unreported from Food

“…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].…”

“…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].…”

Annotating public fungal ITS sequences from the built environment according to the MIxS-Built Environment standard – a report from a May 23-24, 2016 workshop (Gothenburg, Sweden)

“…The taxonomic composition of indoor fungal communities tends to reflect the local outdoor communities, although the majority of fungal particles found indoors is thought to represent spores, hyphal fragments, and other dormant and passively distributed stages (Seo et al 2015). Although most of the fungi recovered from indoor environments would not be able to live in the built environment for any extended period of time, a minority of these species are able to cope with, and will even thrive in, the harsh conditions that the built environment presents (Hamada and Abe 2010;Nevalainen et al 2015;Zupančič et al 2016). These species are mainly saprotrophic, and their degree of active growth largely depends on water availability (Adams et al 2013).…”