High prevalence of the neurotrope Exophiala dermatitidis and related oligotrophic black yeasts in sauna facilities

From Glacier to Sauna: RNA-Seq of the Human Pathogen Black Fungus Exophiala dermatitidis under Varying Temperature Conditions Exhibits Common and Novel Fungal Response

Exophiala dermatitidis (Wangiella dermatitidis) belongs to the group of the so-called black yeasts. Thanks in part to its thick and strongly melanized cell walls, E. dermatitidis is extremely tolerant to various kinds of stress, including extreme pH, temperature and desiccation. E. dermatitidis is also the agent responsible for various severe illnesses in humans, such as pneumonia and keratitis, and might lead to fatal brain infections. Due to its association with the human environment, its poly-extremophilic lifestyle and its pathogenicity in humans, E. dermatitidis has become an important model organism. In this study we present the functional analysis of the transcriptional response of the fungus at 1°C and 45°C, in comparison with that at 37°C, for two different exposition times, i.e. 1 hour and 1 week. At 1°C, E. dermatitidis uses a large repertoire of tools to acclimatize, such as lipid membrane fluidization, trehalose production or cytoskeleton rearrangement, which allows the fungus to remain metabolically active. At 45°C, the fungus drifts into a replicative state and increases the activity of the Golgi apparatus. As a novel finding, our study provides evidence that, apart from the protein coding genes, non-coding RNAs, circular RNAs as well as fusion-transcripts are differentially regulated and that the function of the fusion-transcripts can be related to the corresponding temperature condition. This work establishes that E. dermatitidis adapts to its environment by modulating coding and non-coding gene transcription levels and through the regulation of chimeric and circular RNAs.

Antifungal susceptibility and phenotypic characterization of oral isolates of a black fungus from a nasopharyngeal carcinoma patient under radiotherapy

Background

During a research project on fungal Candida species in patients wearing obturator treated with radiotherapy for their recurrent nasopharyngeal carcinoma, we serendipitously observed the presence of black fungus in two consecutive samples from a patient.

Case presentation

The samples were collected from a 57 year-old Hong Kong gentleman who diagnosed to have undifferentiated type of nasopharyngeal carcinoma. He was treated with definitive concurrent chemoradiotherapy followed by adjuvant chemotherapy and then received a second-course radiotherapy with IMRT. 18S rDNA sequencing revealed that the isolates belong to Exophiala dermatitidis which was susceptible to fluconazole, itraconazole, ketoconazole and voriconazole. Interestingly, E. dermatitidis isolates were resistant to caspofungin and one isolate was resistant to amphotericin B. Both isolates formed biofilms comparable to that of Candida albicans. Single isolate of E. dermatitidis showed hemolysin and proteinase ability comparable to C. albicans whilst the other isolate was not.

Conclusion

We, for the first time, reported the discovery of a black fungus–E. dermatitidis isolates derived from a patient with nasopharyngeal carcinoma treated with radiotherapy. These isolates were shown to be resistant to caspofungin, a major antifungal agent for systemic candidiasis. As little is known about the black fungus in the clinical setting, it is important that clinicians must keep abreast of the new discovery in this field.

Microbial Contamination of Drinking Water and Human Health from Community Water Systems

A relatively short list of reference viral, bacterial and protozoan pathogens appears adequate to assess microbial risks and inform a system-based management of drinking waters. Nonetheless, there are data gaps, e.g. human enteric viruses resulting in endemic infection levels if poorly performing disinfection and/or distribution systems are used, and the risks from fungi. Where disinfection is the only treatment and/or filtration is poor, cryptosporidiosis is the most likely enteric disease to be identified during waterborne outbreaks, but generally non-human-infectious genotypes are present in the absence of human or calf fecal contamination. Enteric bacteria may dominate risks during major fecal contamination events that are ineffectively managed. Reliance on culture-based methods exaggerates treatment efficacy and reduces our ability to identify pathogens/indicators; however, next-generation sequencing and polymerase chain reaction approaches are on the cusp of changing that. Overall, water-based Legionella and non-tuberculous mycobacteria probably dominate health burden at exposure points following the various societal uses of drinking water.

Candida and Fusarium species known as opportunistic human pathogens from customer-accessible parts of residential washing machines

Energy constraints have altered consumer practice regarding the use of household washing machines. Washing machines were developed that use lower washing temperatures, smaller amounts of water and biodegradable detergents. These conditions may favour the enrichment of opportunistic human pathogenic fungi. We focused on the isolation of fungi from two user-accessible parts of washing machines that often contain microbial biofilms: drawers for detergents and rubber door seals. Out of 70 residential washing machines sampled in Slovenia, 79% were positive for fungi. In total, 72 strains belonging to 12 genera and 26 species were isolated. Among these, members of the Fusarium oxysporum and Fusarium solani species complexes, Candida parapsilosis and Exophiala phaeomuriformis represented 44% of fungi detected. These species are known as opportunistic human pathogens and can cause skin, nail or eye infections also in healthy humans. A machine learning analysis revealed that presence of detergents and softeners followed by washing temperature, represent most critical factors for fungal colonization. Three washing machines with persisting malodour that resulted in bad smelling laundry were analysed for the presence of fungi and bacteria. In these cases, fungi were isolated in low numbers (7.5 %), while bacteria Micrococcus luteus, Pseudomonas aeruginosa, and Sphingomonas species prevailed.

Cerebral phaeohyphomycosis by Exophiala dermatitidis

Cerebral phaeohyphomycosis is a rare and frequently fatal disease. We report a case of cerebral phaeohyphomycosis caused by Exophiala dermatitidis in a young immuno competent male presenting to a tertiary care hospital in Jaipur.

Black yeast diversity on creosoted railway sleepers changes with ambient climatic conditions

The environmental isolation of opportunistic pathogenic black yeasts, which are responsible for a wide spectrum of human infections, is essential to understanding the ecology of clinical fungi. Extreme outdoor environments polluted with aromatic hydrocarbons support the growth of black yeasts in unlikely places, such as railway sleepers. However, there are limited data concerning the diversity of these fungi growing on polluted railway sleepers. In this investigation, we examined 845 railway sleeper samples, obtained from 11 Turkish cities representing altitudes from 25 to 1,893 m, and inoculated the samples onto mycological media for the isolation of black yeasts. Ninety-four samples (11.1 %) yielded positive results for black yeast, with creosoted oak sleepers having a significantly higher number of isolates than concrete sleepers (p < 0.05). Identification based on the ribosomal DNA (rDNA) internal transcribed spacer region revealed the highest prevalence of Exophiala phaeomuriformis, followed by Exophiala dermatitidis, Exophiala heteromorpha, Exophiala xenobiotica, and Exophiala crusticola. This study revealed that railway sleepers harboring black yeasts were predominantly (>75 %) populated with thermophilic species. We observed that altitude might have a significant effect on species diversity. Briefly, E. phaeomuriformis exhibited growth over a wide altitude range, from 30 to 1,893 m. In contrast, E. dermatitidis had a remarkable aversion to low altitudes and exhibited maximum growth at 1,285 m. In conclusion, we speculate that one can predict what species will be found on railway sleepers and their probability and that species diversity primarily depends on sleeper type and altitude height. We believe that this study can contribute new insights into the ecology of black yeasts on railway sleepers and the railway factors that influence their diversity.

Nothing special in the specialist? Draft genome sequence of Cryomyces antarcticus, the most extremophilic fungus from Antarctica

The draft genome of the Antarctic endemic fungus Cryomyces antarcticus is presented. This rock inhabiting, microcolonial fungus is extremely stress tolerant and it is a model organism for exobiology and studies on stress resistance in Eukaryots. Since this fungus is a specialist in the most extreme environment of the Earth, the analysis of its genome is of important value for the understanding of fungal genome evolution and stress adaptation. A comparison with Neurospora crassa as well as with other microcolonial fungi shows that the fungus has a genome size of 24 Mbp, which is the average in the fungal kingdom. Although sexual reproduction was never observed in this fungus, 34 mating genes are present with protein homologs in the classes Eurotiomycetes, Sordariomycetes and Dothideomycetes. The first analysis of the draft genome did not reveal any significant deviations of this genome from comparative species and mesophilic hyphomycetes.

Emerging pathogen in immunocompromised hosts: Exophiala dermatitidis mycosis in graft-versus-host disease

Infection with the dematiaceous environmental fungus Exophiala, an emerging pathogen in immunocompromised individuals, poses a diagnostic and therapeutic challenge. Herein, we report the first Exophiala dermatitidis fungemia case, to our knowledge, in an allogeneic hematopoietic stem cell transplant patient with graft-versus-host disease, expanding the clinical setting where Exophiala species mycosis should be suspected.

Comparative genomic and transcriptomic analysis of wangiella dermatitidis, a major cause of phaeohyphomycosis and a model black yeast human pathogen

Black or dark brown (phaeoid) fungi cause cutaneous, subcutaneous, and systemic infections in humans. Black fungi thrive in stressful conditions such as intense light, high radiation, and very low pH. Wangiella (Exophiala) dermatitidis is arguably the most studied phaeoid fungal pathogen of humans. Here, we report our comparative analysis of the genome of W. dermatitidis and the transcriptional response to low pH stress. This revealed that W. dermatitidis has lost the ability to synthesize alpha-glucan, a cell wall compound many pathogenic fungi use to evade the host immune system. In contrast, W. dermatitidis contains a similar profile of chitin synthase genes as related fungi and strongly induces genes involved in cell wall synthesis in response to pH stress. The large portfolio of transporters may provide W. dermatitidis with an enhanced ability to remove harmful products as well as to survive on diverse nutrient sources. The genome encodes three independent pathways for producing melanin, an ability linked to pathogenesis; these are active during pH stress, potentially to produce a barrier to accumulated oxidative damage that might occur under stress conditions. In addition, a full set of fungal light-sensing genes is present, including as part of a carotenoid biosynthesis gene cluster. Finally, we identify a two-gene cluster involved in nucleotide sugar metabolism conserved with a subset of fungi and characterize a horizontal transfer event of this cluster between fungi and algal viruses. This work reveals how W. dermatitidis has adapted to stress and survives in diverse environments, including during human infections.

Development of IgG antibodies to Exophiala dermatitidis is associated with inflammatory responses in patients with cystic fibrosis

BACKGROUND

The clinical importance of airway colonisation by the fungus Exophiala dermatitidis in patients with cystic fibrosis (CF) is unclear. We have previously shown that E. dermatitidis frequently colonises the airways of patients with CF. The aims of the present study were to determine whether patients who are colonised by E. dermatitidis have detectable fungal antigens in the circulation, develop anti-fungal antibodies, and show signs of inflammation and impaired respiratory function.

METHODS

We collected sputum and serum samples consecutively from 98 sputum-producing patients with CF aged more than 12 years. The serum samples were subjected to bacterial and fungal culturing and analyses for fungal antigens and inflammatory factors.

RESULTS

E. dermatitidis was recovered from 17 (17%) patients, the same isolation rate as for Aspergillus fumigatus. There were no difference regarding the levels of β-glucan in the sera from E. dermatitidis culture-positive and culture-negative patients with CF. Serological analysis revealed significantly higher levels of IgG antibodies to E. dermatitidis cell wall fragments in the E. dermatitidis culture-positive patients. Patients with higher level of E. dermatitidis IgG antibodies were more often colonised with non-tuberculous Mycobacteria, and less often with Staphylococcus aureus. The increased levels of IgG antibodies directed against E. dermatitidis were positively associated with higher white blood cell counts, increased erythrocyte sedimentation rate, pancreatic insufficiency, intravenous antibiotic treatment, and they were negatively associated with respiratory function (FEV1 % predicted). Overall, 4/17 Exophiala-positive patients were diagnosed as having symptomatic infection with E. dermatitidis and were treated with broad-spectrum azoles.

CONCLUSION

E. dermatitidis triggers antibody production and may cause significant airway infection in patients with cystic fibrosis.

Nutritional physiology of a rock-inhabiting, model microcolonial fungus from an ancestral lineage of the Chaetothyriales (Ascomycetes)

Rock-inhabiting black fungi [also microcolonial or meristematic fungi (MCF)] are a phylogenetically diverse group of melanised ascomycetes with distinctive morphological features that confer extensive stress tolerance and permit survival in hostile environments. The MCF strain A95 Knufia petricola (syn. Sarcinomyces petricola) belongs to an ancestral lineage of the order Chaetothyriales (class Eurotiomycetes). K. petricola strain A95 is a rock-inhabiting MCF and its growth requirements were studied using the 96-well plate-based Biolog System under ∼1070 different conditions (osmotic stress, pH growth optima, growth factor requirements and nutrient catabolism). A95 is an osmotolerant, oligotrophic MCF that grows best around pH 5. Remarkably, A95 shows metabolic activity in the absence of added nitrogen, phosphorus or sulphur. Correlations could be drawn between the known nutrient requirements of A95 and what probably is available in sub-aerial systems (rock and other material surfaces). Detailed knowledge of A95's metabolic requirements allowed formulation of a synthetic medium that supports strong fungal growth.

Isolation and screening of black fungi as degraders of volatile aromatic hydrocarbons

Black fungi reported as degraders of volatile aromatic compounds were isolated from hydrocarbon-polluted sites and indoor environments. Several of the species encountered are known opportunistic pathogens or are closely related to pathogenic species causing severe mycoses, among which are neurological infections in immunocompetent individuals. Given the scale of the problem of environmental pollution and the phylogenetic relation of aromate-degrading black fungi with pathogenic siblings, it is of great interest to select strains able to mineralize these substrates efficiently without any risk for public health. Fifty-six black strains were obtained from human-made environments rich in hydrocarbons (gasoline car tanks, washing machine soap dispensers) after enrichment with some phenolic intermediates of toluene and styrene fungal metabolism. Based on ITS sequencing identification, the majority of the obtained isolates were members of the genus Exophiala. Exophiala xenobiotica was found to be the dominant black yeast present in the car gasoline tanks. A higher biodiversity, with three Exophiala species, was found in soap dispensers of washing machines. Strains obtained were screened using a 2,6-dichlorophenol-indophenol (DCPIP) assay, optimized for black fungi, to assess their potential ability to degrade toluene. Seven out of twenty strains tested were able to use toluene as carbon source.

Black yeasts-like fungi isolated from dialysis water in hemodialysis units

Hemodialysis in patients with chronic renal failure promotes the removal of toxic substances, water, and minerals from the body and often takes place in specialized clinics. Microbial contamination of dialysis fluid is a serious problem in therapy. One of the sources of contamination is the water used to prepare the dialysate. In Brazil, legislation regulating the microbiological quality of water for dialysis does not cover waterborne microbes such as Pseudomonas, mycobacteria, and fungi. The aim of the present study was to quantify, isolate, and identify fungi present in water systems in six hemodialysis units in Curitiba, Paraná state, Brazil. Fungi were analyzed by surface plating and membrane filtration. Isolates were identified by morphology, while the dematiaceous fungi were identified by sequencing the rDNA ITS region. It was found that 66 % of the samples presented fungi, while black fungi were present in 46 % of all samples. Twenty-eight isolates from treated water for dialysis and dialysate were identified by sequencing and were found to be Exophiala pisciphila, E. cancerae, E. equina, and Rhinocladiella similis. The presence of dematiaceous fungi may pose a risk for debilitated hospitalized patients.

Identification and typing of isolates of Cyphellophora and relatives by use of amplified fragment length polymorphism and rolling circle amplification

The species diversity and identification of black fungi belonging to Cyphellophora and Phialophora, which colonize and infect human skin and nails, were studied using amplified fragment length polymorphism (AFLP). A total of 76 Cyphellophora and Phialophora isolates were evaluated, and their delimitation was compared to earlier studies using multilocus sequencing. The results of the AFLP analysis and sequencing were in complete agreement with each other. Seven species-specific padlock probes for the most prevalent species were designed on the basis of the ribosomal DNA internal transcribed spacer region, and identification of the respective species could easily be achieved with the aid of rolling circle amplification.

Dishwashers are a major source of human opportunistic yeast-like fungi in indoor environments in Mersin, Turkey

The natural habitat of opportunistic fungal pathogens is outside of the host; therefore, it is crucial to understand their ecology and routes of transmission. In this study, we investigated the presence of black and filamentous fungi in moist indoor environments in the city of Mersin in subtropical Turkey. In total, 177 private dwellings were screened and 893 samples obtained using cotton swabs and moistened with physiological saline from dishwashers, washing machines, refrigerators, bath-tubs, bathroom walls, and shower heads. These were then inoculated onto malt extract agar supplemented with chloramphenicol, followed by incubation at 37°C. Thirty samples (3.4%) were positive for fungi, which were then identified by sequencing the rDNA internal transcribed spacer region. Exophiala dermatitidis was the most common species (23), followed by E. phaeomuriformis (three), Magnusiomyces capitatus (two), and Candida parapsilosis (two). Genotype A of E. dermatitidis (14) was more prevalent than genotypes B (eight) and C (one) and E. phaeomuriformis was also represented by two genotypes. Our findings suggest that dishwashers are a major indoor niche for thermophilic black yeasts. The occurrence of the opportunistic filamentous fungus M. capitatus in dishwashers is consistent with a recent report.

Massive contamination of Exophiala dermatitidis and E. phaeomuriformis in railway stations in subtropical Turkey

In order to reveal the source of contamination of opportunistic fungi, their natural habitat has to be understood. Black yeast-like fungi are abundant in man-made environments, particularly in those that are rich in toxic hydrocarbons such as railway ties. In this study, we investigated the presence of black fungi on creosote-treated oak railway ties and concrete sleepers stained with petroleum oil. Samples were collected at two central stations in Turkish cities, Mersin and Adana, and from Tarsus town station located between these two. The sample locations had subtropical climates. A total of 570 railway samples, including 320 from oak and 250 from concrete, were collected. Cotton swabs moistened with sterile physiological saline were applied to the ties and inoculated onto malt extract agar followed by incubation at 37 °C. Overall, we recovered 97 black yeast-like fungi (17.0 % positive). Sixty-three fungi (19.7 %) were collected from creosote-treated oak, whereas 34 isolates (13.6 %) were derived from concrete; the difference was significant (P = 0.05). Identification using rDNA internal transcribed spacer revealed Exophiala dermatitidis (57.7 %) and Exophiala phaeomuriformis (42.3 %). This study suggested that hydrocarbons enrich these opportunistic black yeasts. An eventual health risk is discussed.

Alteration of protein patterns in black rock inhabiting fungi as a response to different temperatures

Rock inhabiting fungi are among the most stress tolerant organisms on Earth. They are able to cope with different stressors determined by the typical conditions of bare rocks in hot and cold extreme environments. In this study first results of a system biological approach based on two-dimensional protein profiles are presented. Protein patterns of extremotolerant black fungi -Coniosporium perforans, Exophiala jeanselmei - and of the extremophilic fungus -Friedmanniomyces endolithicus - were compared with the cosmopolitan and mesophilic hyphomycete Penicillium chrysogenum in order to follow and determine changes in the expression pattern under different temperatures. The 2D protein gels indicated a temperature dependent qualitative change in all the tested strains. Whereas the reference strain P. chrysogenum expressed the highest number of proteins at 40 °C, thus exhibiting real signs of temperature induced reaction, black fungi, when exposed to temperatures far above their growth optimum, decreased the number of proteins indicating a down-regulation of their metabolism. Temperature of 1 °C led to an increased number of proteins in all of the analysed strains, with the exception of P. chrysogenum. These first results on temperature dependent reactions in rock inhabiting black fungi indicate a rather different strategy to cope with non-optimal temperature than in the mesophilic hyphomycete P. chrysogenum.

Molecular typing and antifungal susceptibility of Exophiala isolates from patients with cystic fibrosis

The black yeast Exophiala dermatitidis is a frequent agent of colonization of the lungs of patients with cystic fibrosis (CF). A total of 71 clinical isolates of Exophiala from 13 patients were identified at the species level by sequencing the internal transcribed spacer (ITS) regions 1 and 2 of the rDNA genes and typed by random amplification of polymorphic DNA (RAPD), using two different primers, BG-2 and ERIC-1. In vitro susceptibility of these isolates to some systemic antifungal drugs was investigated using the CLSI method. Almost all the isolates were identified as E. dermatitidis, but long-term colonization with the closely related species E. phaeomuriformis was observed in one patient. No clustering was found according to the geographical origin of the isolates, the isolation date or the antifungal susceptibility. Variations were seen in the susceptibility of studied isolates to antifungals but most of them exhibited low susceptibility to amphotericin B and although some patients were successively colonized by two distinct genotypes, most of the isolates were distributed in patient-specific clusters. This phenomenon may be due to genomic variations of E. dermatitidis in the lung environment of CF patients. These results are typical of colonization of the airways of patients by a poorly distributed environmental fungus, which occupies particular reservoirs that need to be defined.

Dishwashers--a man-made ecological niche accommodating human opportunistic fungal pathogens

Habitats in human households may accommodate microorganisms outside the common spectrum of ubiquitous saprobes. Enrichment of fungi that may require specific environmental conditions was observed in dishwashers, 189 of which were sampled in private homes of 101 towns or communities. One-hundred-two were sampled from various localities in Slovenia; 42 from other European countries; 13 and 3 from North and South America, respectively; 5 from Israel; 10 from South Africa; 7 from Far East Asia; and 7 from Australia. Isolation was performed on samples incubated at 37°C. Species belonging to genera Aspergillus, Candida, Magnusiomyces, Fusarium, Penicillium and Rhodotorula were found occasionally, while the black yeasts Exophiala dermatitidis and Exophiala phaeomuriformis (Chaetothyriales) were persistently and most frequently isolated. Sixty-two percent of the dishwashers were positive for fungi, and 56% of these accommodated Exophiala. Both Exophiala species are known to be able to cause systemic disease in humans and frequently colonize the lungs of patients with cystic fibrosis. We conclude that high temperature, high moisture and alkaline pH values typically occurring in dishwashers can provide an alternative habitat for species also known to be pathogenic to humans.

Sample preparation and 2-DE procedure for protein expression profiling of black microcolonial fungi

The ecology and stress adaptation of black rock inhabiting fungi in hot and cold extreme environments are not yet well understood. Two-dimensional gel electrophoresis (2-DE) is a promising tool to study the protein expression profiling and the metabolic status of microorganisms under stress conditions. The sample preparation has been shown to be the bottleneck for high resolution protein separation in 2-DE. For this purpose conditions must be optimized to obtain reliable and reproducible results. In addition, due to a multilayered and strongly melanized cell wall of black microcolonial fungi, special protocols for cell disruption and processing are required. In the present study, the protocol for protein extraction was established and optimized for the black yeast Exophiala jeanselmei MA 2853. The same protocol was successfully examined also for the meristematic fungus Coniosporium perforans MA 1299. Among the three procedures evaluated, trichloroacetic acid (TCA) precipitation, TCA/acetone precipitation, and phenol extraction combined with methanol/ammonium acetate precipitation, the latter showed to be the best method for black yeasts and meristematic fungi. Penicillium chrysogenum was used as reference strain.

Melanized fungi in human disease

Melanized or dematiaceous fungi are associated with a wide variety of infectious syndromes, including chromoblastomycosis, mycetoma, and phaeohyphomycosis. [corrected]. Many are soil organisms and are generally distributed worldwide, though certain species appear to have restricted geographic ranges. Though they are uncommon causes of disease, melanized fungi have been increasingly recognized as important pathogens, with most reports occurring in the past 20 years. The spectrum of diseases with which they are associated has also broadened and includes allergic disease, superficial and deep local infections, pneumonia, brain abscess, and disseminated infection. For some infections in immunocompetent individuals, such as allergic fungal sinusitis and brain abscess, they are among the most common etiologic fungi. Melanin is a likely virulence factor for these fungi. Diagnosis relies on careful microscopic and pathological examination, as well as clinical assessment of the patient, as these fungi are often considered contaminants. Therapy varies depending upon the clinical syndrome. Local infection may be cured with excision alone, while systemic disease is often refractory to therapy. Triazoles such as voriconazole, posaconazole, and itraconazole have the most consistent in vitro activity. Further studies are needed to better understand the pathogenesis and optimal treatment of these uncommon infections.

Characteristics of pathogenic fungi and antifungal therapy in cystic fibrosis

A defective mucociliary clearance facilitates colonization with bacteria and fungal spores in cystic fibrosis patients. Yeasts and molds are cultured from the cystic fibrosis respiratory tract and often their clinical relevance is unknown. Candida spp. are the most commonly isolated yeasts, whereas Aspergillus spp., Scedosporium apiospermum, as well as Exophiala dermatitidis in some countries, are the most frequent molds recovered from respiratory specimens. Molecular biotyping studies have revealed that some fungal genotypes are capable of chronically colonizing the airways. Persistent Aspergillus fumigatus infection is associated with an increased risk of pulmonary exacerbations requiring hospitalization. The prevalence of non-Aspergillus molds may be underestimated due to overgrowth of Pseudomonas and Aspergillus spp. on routine media. Allergic bronchopulmonary aspergillosis is usually treated by oral steroids and an antifungal azole drug. Interactions with the co-medication have to be considered. A small number of antifungal pharmacokinetic studies indicate a high inter-subject variability for itraconazole, voriconazole and posaconazole, and therefore therapeutic drug monitoring is recommended.

Comparison of fungi found in bathrooms and sinks

To identify the pathogenic fungi present in bathrooms, the growth of fungi collected from the drains of bathrooms was studied at various temperatures and compared with that of fungi from kitchen sink drains. Only a small number of fungi from bathrooms and sinks grew on media incubated at 37 degrees C, at which temperature the fungal count was about 1/600 of that at 25 degrees C. Although hot water is used more frequently in bathrooms than in sinks, the fungal counts at 37 degrees C were similar for bathrooms and sinks. Five species of fungus that can grow at 37 degrees C and were found to grow prolifically in bathrooms were identified using DNA and morphological analysis. In both bathrooms and sinks, Exophiala dermatitidis was predominant in culture at 37 degrees C. Moreover, E. dermatitidis grew at 40 degrees C and used surfactant as a nutrient. Thermotolerant fungi appear to inhabit bathrooms and all residential water appliances.

Elucidation of distribution patterns and possible infection routes of the neurotropic black yeast Exophiala dermatitidis using AFLP

Distribution of populations of the opportunistic black yeast Exophiala dermatitidis was studied using AFLP. This fungus has been hypothesized to have a natural habitat in association with frugivorous birds and bats in the tropical rain forest, and to emerge in the human-dominated environment, where it occasionally causes human pulmonary or fatal disseminated and neurotropic disease. The hypothesis of its natural niche was investigated by comparing a set of 178 strains from natural and human-dominated environments in Thailand with a worldwide selection of 107 strains from the reference collection of the CBS Fungal Biodiversity Centre, comprising 75.7% clinical isolates. Many isolates had unique AFLP patterns and were too remote for confident comparison. Eight populations containing multiple isolates could be distinguished, enabling determination of geographic distributions of these populations. Some of the populations were confined to Thailand, while others occurred worldwide. The local populations from Thailand contained strains from natural and urban environments, suggesting an environmental jump of the fungus. Strains from human brain belonged to widely dispersed populations. In some cases cerebral isolates were identical to isolates from the human intestinal tract. The possibility of cerebral infection through intestinal translocation was thus not excluded.

Indoor wet cells harbour melanized agents of cutaneous infection

The biota of black fungi in humid indoor environments was established using a protocol that consisted of non-selective and selective isolation procedures. In total, 113 samples were taken from bathrooms of residences in The Netherlands, Germany and Austria. Samples were processed either (i) directly by culturing on agar media, or (ii) by pre-incubating samples for enrichment in mineral solutions with perlite granules under constant toluene atmosphere for three months. Dilutions from the latter were then cultured and incubated as were those directly plated to agar media. Black colonies were selected and identified by sequencing the rDNA Internal Transcribed Spacer (ITS) region. Twenty-eight strains of black fungi were found in 26 positive samples without enrichment, and 42 strains were isolated from 38 positive samples after enrichment in toluene. The great majority of black fungal species were members of the order Chaetothyriales, which is the main order of melanized human opportunistic pathogens. Cladosporium species (Capnodiales) were the most frequent isolates when no enrichment was applied, as opposed to Exophiala species (Chaetothyriales) with enrichment. The enrichment method provides insight into a fungal biota commonly occurring in homes which has previously been overlooked. Several species have been previously known only from cutaneous infections and could suggest that bathrooms are a likely reservoir of these fungi.

Isolation and identification of black yeasts by enrichment on atmospheres of monoaromatic hydrocarbons

Black yeast members of the Herpotrichiellaceae present a complex ecological behavior: They are often isolated from rather extreme environments polluted with aromatic hydrocarbons, while they are also regularly involved in human opportunistic infections. A selective technique to promote the in vitro growth of herpotrichiellaceous fungi was applied to investigate their ecophysiology. Samples from natural ecological niches and man-made environments that might contain black yeasts were enriched on an inert solid support at low humidity and under a controlled atmosphere rich in volatile aromatic hydrocarbons. Benzene, toluene, and xylene were provided separately as the sole carbon and energy source via the gas phase. The assayed isolation protocol was highly specific toward mesophilic Exophiala species (70 strains of this genus out of 71 isolates). Those were obtained predominantly from creosote-treated railway ties (53 strains), but isolates were also found on wild berries (11 strains) and in guano-rich soil samples (six strains). Most of the isolates were obtained on toluene (43 strains), but enrichments on xylene and benzene also yielded herpotrichiellaceous fungi (17 and 10 isolates, respectively). Based upon morphological characterizations and DNA sequences of the full internal transcriber spacers (ITS) and the 8.5S rRNA genes, the majority of the obtained isolates were affiliated to the recently described species Exophiala xenobiotica (32 strains) and Exophiala bergeri (nine strains). Members of two other phylogenetic groups (24 and two strains, respectively) somewhat related to E. bergeri were also found, and a last group (three strains) corresponded to an undescribed Exophiala species.

The changing microbial epidemiology in cystic fibrosis

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Rapid screening for genotypes as possible markers of virulence in the neurotropic black yeast Exophiala dermatitidis using PCR-RFLP

A simple method for fungal genotype screening was developed for the black yeast Exophiala dermatitidis based on RFLP of ribosomal ITS regions currently used as potential virulence markers. In a study set of 502 strains of the species, two main genotypes were recognized. Only 0.97% of lanes were difficult to interpret as they did not clearly present one of the expected genotypes. Twenty strains were deviating and proved to be E. spinifera after sequencing. Eight common, related species (based on SSU data) with clinical significance yielded different patterns with TaqI digestion, and thus the method is also usable for routine diagnostics.

Systemic phaeohyphomycosis resembling primary sclerosing cholangitis caused by Exophiala dermatitidis

Exophiala dermatitidis, one of the saprophytic dematiaceous fungi, is a cause of local and disseminated phaeohyphomycosis. We report a case of systemic phaeohyphomycosis resembling sclerosing cholangitis caused by E. dermatitidis in a 24-year-old woman.

Occurrence and relevance of filamentous fungi in respiratory secretions of patients with cystic fibrosis--a review

The colonization of airways by filamentous fungi and the development of respiratory infections require some predisposing factors as encountered in patients with cystic fibrosis (CF). Indeed, the defective mucociliary clearance which characterizes the disease is associated with local immunological disorders. In addition, the prolonged therapy with antibiotics and the use of corticosteroid treatments also facilitate fungal growth. An important fungal biota has been described in respiratory secretions of patients suffering from CF. Aspergillus fumigatus, Scedosporium apiospermum and Aspergillus terreus for filamentous fungi and Candida albicans for yeasts are the main fungal species associated with CF. Although less common, several fungal species including Aspergillus flavus and Aspergillus nidulans may be isolated transiently from CF respiratory secretions, while others such as Exophiala dermatitidis and Scedosporium prolificans may chronically colonize the airways. Moreover, some of them like Penicillium emersonii and Acrophialophora fusispora are encountered in humans almost exclusively in the context of CF. As fungal complications in CF patients are essentially caused by filamentous fungi the present review will not include works related to yeasts. In CF patients, fungi may sometimes be responsible for deterioration of lung function, as occurs in allergic broncho-pulmonary aspergillosis (ABPA) which is the most common fungal disease in this context. Additionally, although the clinical relevance of the fungal airway colonization is still a matter of debate, filamentous fungi may contribute to the local inflammatory response, and therefore to the progressive deterioration of the lung function.

The neurotropic black yeast Exophiala dermatitidis has a possible origin in the tropical rain forest

The black yeast Exophiala dermatitidis is known as a rare etiologic agent of neurotropic infections in humans, occurring particularly in East and Southeast Asia. In search of its natural habitat, a large sampling was undertaken in temperate as well as in tropical climates. Sampling sites were selected on the basis of the origins of previously isolated strains, and on the basis of physiological properties of the species, which also determined a selective isolation protocol. The species was absent from outdoor environments in the temperate climate, but present at low abundance in comparable habitats in the tropics. Positive outdoor sites particularly included faeces of frugivorous birds and bats, in urban as well as in natural areas. Tropical fruits were found E. dermatitidis positive at low incidence. Of the human-made environments sampled, railway ties contaminated by human faeces and oily debris in the tropics were massively positive, while the known abundance of the fungus in steam baths was confirmed. On the basis of the species' oligotrophy, thermotolerance, acidotolerance, moderate osmotolerance, melanization and capsular yeast cells a natural life cycle in association with frugivorous animals in foci in the tropical rain forest, involving passage of living cells through the intestinal tract was hypothesized. The human-dominated environment may have become contaminated by ingestion of wild berries carrying fungal propagules.

WdStuAp, an APSES transcription factor, is a regulator of yeast-hyphal transitions in Wangiella (Exophiala) dermatitidis

APSES transcription factors are well-known regulators of fungal cellular development and differentiation. To study the function of an APSES protein in the fungus Wangiella dermatitidis, a conidiogenous and polymorphic agent of human phaeohyphomycosis with yeast predominance, the APSES transcription factor gene WdSTUA was cloned, sequenced, disrupted, and overexpressed. Analysis showed that its derived protein was most similar to the APSES proteins of other conidiogenous molds and had its APSES DNA-binding domain located in the amino-terminal half. Deletion of WdSTUA in W. dermatitidis induced convoluted instead of normal smooth colony surface growth on the rich yeast maintenance agar medium yeast extract-peptone-dextrose agar (YPDA) at 37 degrees C. Additionally, deletion of WdSTUA repressed aerial hyphal growth, conidiation, and invasive hyphal growth on the nitrogen-poor, hypha-inducing agar medium potato dextrose agar (PDA) at 25 degrees C. Ectopic overexpression of WdSTUA repressed the convoluted colony surface growth on YPDA at 37 degrees C, and also strongly repressed hyphal growth on PDA at 25 degrees C and 37 degrees C. These new results provide additional insights into the diverse roles played by APSES factors in fungi. They also suggest that the transcription factor encoded by WdSTUA is both a positive and negative morphotype regulator in W. dermatitidis and possibly other of the numerous human pathogenic, conidiogenous fungi capable of yeast growth.

Opportunistic, human-pathogenic species in the Herpotrichiellaceae are phenotypically similar to saprobic or phytopathogenic species in the Venturiaceae

Although morphologically similar, species of Cladophialophora (Herpotrichiellaceae) were shown to be phylogenetically distinct from Pseudocladosporium (Venturiaceae), which was revealed to be synonymous with the older genus, Fusicladium. Other than being associated with human disorders, species of Cladophialophora were found to also be phytopathogenic, or to occur as saprobes on organic material, or in water, fruit juices, or sports drinks, along with species of Exophiala. Caproventuria and Metacoleroa were confirmed to be synonyms of Venturia, which has Fusicladium (= Pseudocladosporium) anamorphs. Apiosporina, based on A. collinsii, clustered basal to the Venturia clade, and appears to represent a further synonym. Several species with a pseudocladosporium-like morphology in vitro represent a sister clade to the Venturia clade, and are unrelated to Polyscytalum. These taxa are newly described in Fusicladium, which is morphologically close to Anungitea, a heterogeneous genus with unknown phylogenetic affinity. In contrast to the Herpotrichiellaceae, which were shown to produce numerous synanamorphs in culture, species of the Venturiaceae were morphologically and phylogenetically more uniform. Several new species and new combinations were introduced in Cladophialophora, Cyphellophora (Herpotrichiellaceae), Exophiala, Fusicladium, Venturia (Venturiaceae), and Cylindrosympodium (incertae sedis).

Isolation of Exophiala dermatitidis from endotracheal aspirate of a cancer patient

Exophiala (Wangiella) dermatitidis is a melanised (darkly pigmented) yeast-like organism that has been reported from the environment and wild animals. The organism is a frequent coloniser of lungs of patients with cystic fibrosis and causes occasional disseminated phaeohyphomycosis and fungaemia. Exophiala dermatitidis is distributed worldwide, but cerebral cases are restricted to East Asia. We report a case of 54-year-old Qatari female patient with a known history of cancer, suffering from pulmonary disorder. Culture of endotracheal aspirate revealed the growth of E. dermatitidis concomitant with Candida krusei. The final diagnosis of E. dermatitidis and attribution to genotype B was achieved by sequencing the rDNA internal transcribed spacer (ITS) region. The present case concerns a pulmonary colonisation by E. dermatitidis, similar to that commonly seen in cystic fibrosis patients. For the detection of E. dermatitidis in clinical specimens culturing techniques are required. The patient finally expired with persistent cancer and C. krusei fungaemia. Review of literature and listing of E. dermatitidis cases published after 1992 show a sharp increase in clinical cases during the 1990s.