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The medically important dematiaceous fungi and their identification.

Dematiaceous fungi include a large group of organisms that are darkly pigmented (dark brown, olivaceous, or black). In most cases the pigment is melanin, and specifically, dihydroxynaphthalene melanin. The diseases produced include chromoblastomycosis, eumycotic mycetoma, and phaeohyphomycosis. Phaeohyphomycosis is a new classification for a diverse group of previously known entities grouped together on the basis of finding dematiaceous hyphal and/or yeast-like forms in tissue; tissue involvement may be superficial, cutaneous and corneal, subcutaneous, or systemic. Identification of these fungi is based mostly upon morphology. Important structures include annellides (Phaeoannellomyces, Exophiala), phialides (Phialophora, Wangiella), adelophialides (Phialemonium without collarettes, Lecythophora with collarettes), differentiation of conidiophores (Xylohypha versus Cladosporium) and conidial hilum, septation and germination (Bipolaris, Drechslera, Exserohilum). Useful laboratory tests include the 12% gelatin test (controversial), nitrate assimilation (W. dermatitidis is negative, most other species are positive), and determination of temperature maxima (especially 37 degrees C for E. jeanselmei, 40 degrees C for W. dermatitidis and B. spicifera, 42 degrees C for X. bantiana, and 45 degrees C for Dactylaria constricta var. gallopava and Scedosporium inflatum).

Fungi↗

Pathogenic fungi in human dwellings.

Airborne invasive fungal infections in various risk groups of people suffering from immunodeficiencies are an increasing problem for modern medicine. Because of the acute and rapid course of invasive infections, prevention is of principal significance. Such prevention mainly concerns the control of fungal spores in indoor air. In this connection the immediate environment offering ecological niches for growth and morphogenesis of infective particles of Aspergillus spp., Mucoraceae, Cryptococcus neoformans and some other yeast-like fungi is of main interest. The current problems of indoor air mycology, i.e. the epidemiology and ecology of pathogenic fungi in indoor air, can only be recognized and interpreted by centres routinely performing mycological diagnosis for all the various risk groups of patients. Models of specific surveillance of the most important fungal pathogens (e.g. Aspergillus spp. and Cryptococcus neoformans) in indoor air will be outlined and discussed.

Air Microbiology↗

Screening of different keratin baits for isolation of keratinophilic fungi.

Twenty different keratin-rich substrates were screened as keratin baits for isolation of keratinophilic fungi from different soil sample of Chhindwara District, India. Fungi easily formed colonies on different baits. However, hair, feathers and horns were found to be more suitable than nails, fish fins and fish scales.

Animals↗

Risk assessment of fungi reported from humans and animals.

A classification of fungi into biosafety categories is proposed, and the criteria for attribution to biosafety levels (BSL) are briefly discussed. The list differs from previous publications on this topic mainly by stressing (ecological) criteria derived from the fungi rather than host factors, and in including all species accepted in the recent medical literature.

Animals↗

[Qualitative and quantitative studies of autofluorescence in fungi].

Fluorescence microscopy is an important method in mycology. It is a common procedure used in immunology or histology and more recently in modern techniques of molecular biology like in-situ hybridization. Since several molds and yeasts show autofluorescence, an interference of this phenomenon with the detection method cannot be excluded. Therefore, we studied autofluorescence in fungi in more detail, in particular with respect to the dependence of this phenomenon from growth conditions, fixing method or mounting medium used. Here we show that moulds cultivated in a liquid medium are strongly autofluorescent which could be considerably reduced by repetitive washing. In moulds, we did not find important differences in autofluorescence levels with the three fixing methods under study. However, this finding cannot be generalized. Thus, in the yeast Candida albicans we found the autofluorescence pattern being largely dependent from the fixing method and the excitation wave length, respectively. In particular, with green excitation we could show that aceton fixation resulted in strong fluorescence of individual cells within a vast population of cells showing little or no autofluorescence. In addition, we could demonstrate that mounting media are able to strongly modify autofluorescence in fungi. Using digital image acquisition with a cooled CCD camera we were able to quantify the influence of different mounting media on fluorescence intensities of Aspergillus fumigatus.

Aspergillus fumigatus↗

[In vitro growth of human pathogenic fungi on different stocking fabrics].

Athlete's foot and onychomycosis can be aggravated due to inappropriate footwear. In this study we examined whether stockings of synthetic and mixed fabrics may influence the growth behaviour of the commonly isolated fungi Trichophyton rubrum, Trichophyton mentagrophytes and Candida albicans. A standardized suspension of each fungus was given to each sample of twelve stockings of different materials. The size of the growing colonies and the velocity of their growth were measured and compared to each other. Based on our data stockings depending on their fabric mixture seem to support or inhibit respectively the growth of fungi. Stockings composed of polyamide and a high percentage of polyurethane (Elasthan) and silk stockings as well may likely promote the fungal growth.

Clothing↗

Keratinophilic fungi on feathers of pigeon in Maharashtra, India.

Results of a preliminary survey of keratinophilic fungi associated with feathers of pigeon on high rise buildings in Thane district of Maharashtra (India) are reported. A total of 100 samples were examined, of which 67 samples were positive for keratinophilic fungi. Altogether 67 fungal strains belonging to 10 species of seven genera were isolated viz. Chrysosporium indicum (24%), Chrysosporium sp. (2%), Chr. tropicum (8%), Chrysosporium state of Arthroderma tuberculatum (3%), Chrysosporium state of Ctenomyces serratus (15%), Malbranchea pulchella (3%), Malbranchea sp. (1%), Microsporum gypseum (5%), Myriodontium keratinophilum (2%) and Trichophyton terrestre (4%).

Animals↗

In vitro antifungal susceptibility testing of filamentous fungi with Sensititre Yeast One.

Sensititre is a colorimetric microdilution method for in vitro antifungal susceptibility testing based on the M27-A document (National Committee for Clinical Laboratory Standards) for yeasts. Difference between both methods is the presence of Alamar-blue and RPMI 1640 (glucose 2%) as culture medium. Antifungal susceptibility to amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine, 100 opportunistic filamentous fungi (Aspergillus spp., Fusarium spp., Scedosporium spp.) obtained from pathological samples was determined by the Sensititre method. Induction to conidium and sporangiospore formation at 35 degrees C was used to get inoculum and plates were covered by 1 ml of saline and suspensions were made by gently probing by a sterile loop. Optical densities of the conidial suspensions were adjusted to 80-82% transmittance for Aspergillus spp. and 68-70% for the rest of strains tested. Final inoculum concentration size was 0.4 x 10(4)-5 x 10(4) CFU ml(-1). Readings were made at 72 h of incubation at 35 degrees C; amphotericin B and itraconazole was active against Aspergillus fumigatus with CMI90 1 and 0.5 microg ml(-1), respectively, opposite to Scedosporium prolificans and Scedosporium apiospermum. As it was expected, a CMI90 of 256 microg ml(-1) for fluconazole and CMI90 for flucytosine amounting to 64 g ml(-1) were obtained. Sensititre Yeast One is a useful method and an alternative to reference methods to determine antifungal susceptibility of filamentous fungi for clinical laboratory routine. Correlation with microdilution results is studied. New triazole derivatives should be included as soon as their clinical use will be feasible.

Amphotericin B↗

Assemblages of ericoid mycorrhizal and other root-associated fungi from Epacris pulchella (Ericaceae) as determined by culturing and direct DNA extraction from roots.

Ericoid mycorrhizal fungal endophytes form mycorrhizal associations with Ericaceae plant taxa and are regarded as essential to the ecological fitness of the plants in extremely nutrient-poor soils worldwide. We isolated fungi from roots of Epacris pulchella (Ericaceae) in a south-eastern Australian sclerophyll forest and compared rDNA internal transcribed spacer (ITS) restriction fragment length polymorphisms (RFLPs) and sequences for the cultured isolate assemblage with fungi identified in DNA extracted directly from the same root systems by cloning or denaturing gradient gel electrophoresis (DGGE). The most abundant RFLP types in the cultured isolate assemblage were identified as putative ericoid mycorrhizal ascomycete endophytes, and these also represented the most abundant RFLP types in the cloned assemblage and the most intense bands in DGGE profiles. Each method identified unique taxa, notably putative basidiomycetes in the DNA extracted directly from E. pulchella roots. However, the relative abundance of these was low.

DNA, Fungal↗

Prevalence of Yeast and fungi other than Candida albicans in the vagina of normal young women.

Yeasts and fungi other than Candida albicans were isolated from the vagina of 86 out of 1498 women (5.7 per cent) who attended a family planning clinic and they comprised 27.7 per cent of all fungal species obtained. These fungi were significantly more common in women aged 35 years and over and in those who used the diaphragm than in others. They were no more common in women with an abnormal vaginal discharge on examination than in others; and they were no more common in women with genitourinary symptoms than in women without.

Adolescent↗

Vegetable sponge as a matrix to immobilize micro-organisms: a trial study for hyphal fungi, yeast and bacteria.

The vegetable sponge of Luffa cylindrica was studied as a matrix for the immobilization of hyphal fungi, yeast and bacteria. All were observed to be entrapped within the sponge. When the various immobilized systems were subcultured in their respective fresh nutrient media, the hyphal fungi showed an increase in biomass with no cellular release and secondary colony formation. The immobilized yeast and bacteria released cells into the medium. Advantages of the reticulated biostructure as an immobilization matrix are discussed.

Bacteria↗

Nitrification in vitro by a range of filamentous fungi and yeasts.

A wide range of fungi including yeasts, growing on Czapek Dox medium, nitrified added ammonium and the ammonium released by urea hydrolysis. Phanerochaete chrysosporium and Hymenoscyphus ericiae were the only fungi tested which failed to nitrify. A soil yeast (isolate 1) was the most active nitrifier of ammonium in vitro, forming 0.80 microgram nitrate mg-1 biomass over the 7 d incubation period.

Biomass↗

Effect of coumarin on glucose uptake by anaerobic rumen fungi in the presence and absence of Methanobrevibacter smithii.

The effect of coumarin (1,2 benzopyrone) on glucose utilisation by the anaerobic rumen fungi Neocallimastix frontalis and N. patriciarum has been compared with the effect of p-coumaric acid. Both compounds largely inhibited glucose utilisation by N. patriciarum strain Cx when present in the medium at a concentration of 2.5 mM, and had a similar effect on N. frontalis strain RE1 at 5 mM. Although in earlier studies co-culturing rumen fungi with Methanobrevibacter smithii enhanced resistance to ionophores, no comparable protective effect of M. smithii was found in the present study.

Animals↗

Interactions between killer yeasts and pathogenic fungi.

A total of 17 presumptive killer yeast strains were tested in vitro for growth inhibitory and killing activity against a range of fungal pathogens of agronomic, environmental and clinical significance. Several yeasts were identified which displayed significant activity against important pathogenic fungi. For example, isolates of the opportunistic human pathogen, Candida albicans, were generally very sensitive to Williopsis mrakii killer yeast activity, whilst killer strains of Saccharomyces cerevisiae and Pichia anomala markedly inhibited the growth of certain wood decay basidiomycetes and plant pathogenic fungi. Results indicate that such yeasts, together with their killer toxins, may have potential as novel antimycotic biocontrol agents.

Antifungal Agents↗

Novel aliphatic epoxide hydrolase activities from dematiaceous fungi.

Epoxide hydrolases were found to be constitutively expressed in dematiaceous fungi coincident with secondary metabolite pigment production in stationary or idiophase. Washed-cell preparations of two fungi, Ulocladium atrum CMC 3280 and Zopfiella karachiensis CMC 3284, exhibited affinity for 2,2-dialkylated oxiranes, for which contrasting enantioselectivities were observed, but not for aromatic styrene oxide or alicyclic cyclohexene oxide type substrates. Lyophilised preparations of soluble epoxide hydrolase activities proved to be effective catalysts for the mild hydrolysis of aliphatic epoxides.

Biotransformation↗

The effect of culture conditions on the mycelial growth and luminescence of naturally bioluminescent fungi.

The effects of temperature, light and pH on mycelial growth and luminescence of four naturally bioluminescent fungi were investigated. Cultures of Armillaria mellea, Mycena citricolor, Omphalotus olearius and Panellus stipticus were grown at 5 degrees C, 15 degrees C, 22 degrees C and 30 degrees C, under 24 h light, 12 h light/12 h dark and 24 h dark, and at a pH ranging from 3.5 to 7 in three separate experiments. Temperature and pH had a significant effect on mycelial growth and bioluminescence, however light did not. Bioluminescence and mycelial growth were optimum at 22 degrees C and pH 3-3.5, the exception being M. citricolor for which bioluminescence and growth were optimum at pH 5-6 and pH 4, respectively. With the exception of M. citricolor, bioluminescence and mycelial growth were greater under 24 h darkness. An understanding of the effect of culture conditions on mycelial growth and luminescence is necessary for the future application of bioluminescent fungi as biosensors.

Fungi↗

Degradation of pyrene by indigenous fungi from a former gasworks site.

Indigenous fungi isolated from soil of a former gasworks site were investigated in submerged cultures with pyrene as the sole carbon source. Five fungal strains capable of degrading pyrene included one strain of Trichoderma harzianum and four strains with characteristics of the genus Penicillium. These are identified as Penicillium simplicissimum, Penicillium janthinellum, Penicillium funiculosum and Penicillium terrestre. A maximum of 75% of 50 mg l(-1) and 67% of 100 mg l(-1) of pyrene was removed by the fast degrading strain P. terrestre at 22 degrees C during 28 days of incubation. The slower degrader P. janthinellum was able to remove 57% of 50 mg l(-1) and about 31.5% of 100 mg l(-1) pyrene. Degradation of pyrene is directly correlated with biomass development. To the best of our knowledge, this is the first time that fungi have been reported to use pyrene as the sole carbon and energy source. They may be ideal candidates for effective bioremediation of polycyclic aromatic hydrocarbons.

Biodegradation, Environmental↗

Extracellular and cellular mechanisms sustaining metal tolerance in ectomycorrhizal fungi.

This review focuses on recent evidence that identifies potential extracellular and cellular mechanisms that may be involved in the tolerance of ectomycorrhizal fungi to excess metals in their environment. It appears likely that mechanisms described in the nonmycorrhizal fungal species are used in the ectomycorrhizal fungi as well. These include mechanisms that reduce uptake of metals into the cytosol by extracellular chelation through extruded ligands and binding onto cell-wall components. Intracellular chelation of metals in the cytosol by a range of ligands (glutathione, metallothioneins), or increased efflux from the cytosol out of the cell or into sequestering compartments are also key mechanisms conferring tolerance. Free-radical scavenging capacities through the activity of superoxide dismutase or production of glutathione add another line of defence against the toxic effect of metals.

Chelating Agents↗