Environmental characteristics and taxonomy of microscopic fungi isolated from washing machines

Abstract

Washing machines (WMs) are convenient places for fungal colonization. This study is focused on fungal diversity of WMs, and investigates relationships between habits of WM users and colonising species. Housekeeping conditions and habits were assessed in Hungary with a questionnaire. Several fungal species were identified by microscopy and sequence analysis of diagnostic loci. Based on the results, 32 % of the sampled WMs were highly polluted with various species of fungi. Forty six percent of them were colonised also by opportunistically human pathogenic species. In total, 32 yeast and 39 filamentous fungal strains were isolated. Growth tests were conducted with five selected taxa (Cutaneotrichosporon dermatis, Cystobasidium slooffiae, Meyerozyma guilliermondii, Candida parapsilosis and the Fusarium oxysporum species complex (FOSC)) to ascertain their tolerance ranges. None of the examined isolates were able to grow >50 C, 4.10 < pH < 10.88. FOSC could grow at high salinity. More species were detected in WMs operated in rooms without heating systems (p ¼ 0.0025). The number of species was higher in WMs located in the kitchen than the ones kept in bathroom or in other rooms (p ¼ 0.0205). WMs may serve as a reservoir of pathogenic fungi, the presence of which may depend on the usage of these devices.

Mycological Investigation of Bottled Water Dispensers in Healthcare Facilities

“…Counts of fungi in BWDs showed positive correlation with pH (range: 7.1–10.8). This finding is in contradiction to our previous results, where fungal counts of washing machines showed negative correlation with pH (range: 7–10.9) [ 9 ]. Low pH in washing machines is possibly due to the use of detergents, but such chemicals are not applied in BWDs.…”

“…Contrariwise to BWDs, pathogenic Candida spp. were found to be common in domestic washing machines in Hungary [ 9 , 40 ]. Candida species occurred frequently in such water-connected devices, mostly in hardly accessible parts of them.…”

“…Fungal contamination of water contained in modern household devices, such as washing machines [ 9 ] and dishwashers [ 10 , 11 ] have attracted attention in the last decade, as they provide new habitats for microscopic fungi. Bottled water dispensers (BWDs, also known as water coolers, Figure 1 ) were rarely studied, the only study on them was carried out by Yamaguchi et al [ 12 ] in residents and office buildings in Brazil.…”

Screening Mold Colonies by Using Two Toxicity Assays Revealed Indoor Strains of Aspergillus calidoustus Producing Ophiobolins G and K

“…The A. calidoustus MH34 ITS sequence is deposited in GenBank (KM853016.1). Although ITS sequence analysis alone is not able to discriminate between the species A. calidoustus and A. pseudodeflectus, the presence of Hülle cells clearly confirms the ITS-based diagnosis of strain MH34 as A. calidoustus, as A. pseudodeflectus is not forming any Hülle cells [33].…”

“…The reference strains A. westerdijkiae PP2 and A. versicolor SL/3 were identified at DSMZ (Deutche Samlung vor Mikroorganismen und Zellkulturen) in 2004 and 2008, respectively. Aspergillus calidoustus MH34, Trichoderma atroviride Tri335, and Chaetomium globosum HS5 were identified based on the amplification of the internal transcribed spacer (ITS1-5.8S rDNA-ITS2) region of the ribosomal RNA gene cluster with primers ITS1 (5 -TCCGTAGGTGAACCTGCGG-3 ) and ITS4 (5 -TCCTCCGCTTATTGATATGC-3 ) [32] based on [33]. The A. calidoustus MH34 ITS sequence is deposited in GenBank (KM853016.1).…”