Fig 1.
Sampling sites in the dishwashers (A-H) and the prevailing taxa on the primary isolation plates (A.1-H.1) cultured from the particular dishwashers sampling sites swab samples.
On rubber seal (A) and detergent dispenser (B) E. dermatitidis genotype A (A.1, B.1, respectively); on rinse-aid dispenser (C) E. dermatitidis genotype A, FDSC, Saprochaete/Magnusiomyces clade (C.1); on sprinkler (D) E. dermatitidis genotype A, E. phaeomuriformis genotype 1 (D.1); on door (E) A. melanogenum, P. crustosum, E. dermatitidis genotype A, C. parapsilosis (E.1); on cutlery rack (F) FOSC, E. phaeomuriformis genotype 1, C. parapsilosis (F.1); in drain (G) E. dermatitidis genotype A, Saprochaete/ Magnusiomyces clade, Meyerozyma guilliermondii, FDSC (G.1); on side nozzles (H) FDSC (H.1). Note: not the actual state of one dishwasher, but a combination of several sampled dishwashers.
Fig 2.
Sampling sites in the kitchens with a dishwasher (A) and the kitchens without a dishwasher (B).
(S) Representative kitchen sink indicating sampling sites of 1 L tap water (filtered through 0.45-μm cellulose membrane filter and incubated on DRBC agar) (1), pipe grid on tap (2), kitchen counter above dishwasher/ near sink (3), and inside kitchen sink (4). Inset (5): Rubber seal from under kitchen sink. (A, B) Representative primary isolation plates cultured from kitchen samples, numbered according to sample site. (A1) A. melanogenum, E. alcalophila, R. similis and C. parapsilosis. (B1) Trichosporon montevideense, R. mucilaginosa, C. parapsilosis and E. phaeomuriformis genotype 1. (A2) E. phaeomuriformis genotype 1 and C. parapsilosis. (B2) E. phaeomuriformis genotype 1. (A3) A. melanogenum, E. phaeomurifomis genotype 2 and R. mucilaginosa. (B3) C. parapsilosis, M. guilliermondii, C. pararugosa and P. kluyveri. (A4) O. constricta, Cysosporidium slooffiae and Metschnikowia pulcherrima. (B4) M. guilliermondii, C. pararugosa and S. cerevisiae. (A5) C. pararugosa, C. parapsilosis, E. dermatitidis genotype A and FOSC. (B5) M. guilliermondii, C. parapsilosis, C. orthopsilosis K. europaea, R. mucilaginosa, E. phaeomuriformis genotype 1 and A. melanogenum.
Table 1.
Diversity and frequency of the fungi isolated in the present study from tap water, waste water, aerosols, dishwashers and kitchen surfaces.
Table 2.
Frequency of occurrence of strains and their sampling sites and GenBank accession numbers from the 30 residential dishwashers sampled in the present study.
Table 3.
Comparison of occurrence (%) of selected opportunistic pathogenic fungi in 9 locations of 30 residential dishwashers, sampled in the present study.
Table 4.
Occurrence (%) of selected opportunistic pathogenic fungi in kitchens without and with dishwashers.
Fig 3.
Representative samples from biofilm formed on dishwasher rubber seal.
(a-f) Dehydrated biofilm. (a, b, f) In-vivo morphology (muriform cells embedded in extracellular polymeric substance (EPS)) from a biofilm on a dried rubber dishwasher seal from which E. dermatitidis genotypes A and C were isolated. (c-e) Structures of filamentous fungi after desiccation show Fusarium spp. (c), Aspergillus spp. (d) and spores (e). (g-i) Hydrated biofilm. Co-culture of bacteria and fungi (g), clusters of yeast cells covered with EPS, with additional individual cells that spread during the washing cycle (h), and muriform cells of E. dermatitidis genotype A with fungal hyphae (i).
Fig 4.
Orders of fungi identified from the hydrated and dehydrated biofilms.
Left: The hydrated biofilm samples contained six different orders of fungi, as mainly Filobasidiales (especially genus Cryptococcus; Basidiomycota), Sporidiobolales (genus Rhodotorula; Basidiomycota) and Saccharomycetales (genus’s Saccharomyces, Hanseniaspora, Debaryomyces; all belong to the Ascomycota). Right: The dehydrated biofilms contained nine different orders of fungi, as mainly Hypocreales (including different moulds and genus Fusarium; Ascomycota), Eurotiales (genus’s Aspergillus, Penicillium, Talaromyces; all belong to the Ascomycota) and Xylariales (genus Hansfordia; Ascomycota). Both hydrated and dehydrated biofilms contained Chaerothyriales (E. dermatitidis) (0.07%, 1.77%, respectively) and Sordariomycetes (F. dimerum) (0.3%, 0.35%, respectively).
Fig 5.
Relative mean percentages (±standard deviation) of the seven opportunistic fungal pathogens most commonly isolated from the kitchen surfaces.