Exophiala amphawaensis sp. nov., a novel black yeast isolated from the gut of amphipods in Thailand

The genus Exophiala is polymorphic, able to transition between yeast, hyphal and pseudohyphal forms. Species of the genus Exophiala are ubiquitous fungi that are distributed in various environments around the world. During a survey of fungal diversity in the gut of amphipods (Floresorchestia amphawaensis and undescribed Dogielinotid amphipods) from the Amphawa estuary, Samut Songkhram province, Thailand, five black yeast strains (DMKU-MG01, DMKU-MG07, DMKU-MG08, DMKU-HG10 and DMKU-FG04) were identified as representing a novel taxon on the basis of a combination of morphological and molecular phylogenetic features. The five strains did not produce filamentous hyphae or pseudohyphae. Only budding yeast cells were observed. On the basis of the phenotypic characteristics and the results of molecular analyses of the D1/D2 region of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) region, the five strains were identified as representing a novel species via applied nucleotide pairwise analysis. They differed from the most closely related species Exophiala alcalophiala by 3.54 % nucleotide substitutions (20 nucleotide substitutions in 572 bp) in the D1/D2 domains of the LSU rRNA gene. Moreover, the sequences of the ITS region of the five strains differed from those of the most closely related species E. alcalophiala, by 7.44-9.62 % nucleotide substitutions, and Exophiala halophiala, by 7.2-7.53 % nucleotide substitutions. The results of phylogenetic analyses based on the concatenated sequences of the ITS regions and the D1/D2 domains of the LSU rRNA gene confirmed that the five black yeast strains represented a single novel species of the genus Exophiala. In this study, Exophiala amphawaensis sp. nov. is proposed to accommodate these strains. The holotype is TBRC 15626T and the isotype is PYCC9020. The MycoBank accession number of the novel species is MB 851477.

Exophiala angulospora infection in hatchery-reared lumpfish (Cyclopterus lumpus) broodstock

Samples from moribund lumpfish were collected in a marine hatchery in Scotland in 2015. Black nodules were noted on the skin, and gills and fungal hyphae were extensively distributed in musculature and internal organs. Multifocal chronic inflammatory lesions displaced structures in all affected organs. Mortalities commenced on completion of spawning in May and were evenly distributed over the second year in the temperature range 11-15°C. The main systemic infection causing agent was initially identified based on morphological characteristics as an Exophiala species. Ribosomal DNA (rDNA) ITS regions of the isolates were subsequently sequenced confirming the isolates belonged to Exophiala genus. All isolates fell in a single phylogenetic cluster, which is represented by Exophiala angulospora. Fish were treated with either formalin or Bronopol or a combination of both, but there was no effect on the pattern or numbers of mortalities. Isolates were also tested against three different concentrations of Latrunculin A, Amphotericin B and Itraconazole with no success. It is of utmost importance to increase the knowledge on pathogen-host interactions to successfully develop sustainable control methods.

A molecular approach for the rapid, selective and sensitive detection of Exophiala jeanselmei in environmental samples: development and performance assessment of a real-time PCR assay

Exophiala jeanselmei is an opportunistic pathogenic black yeast growing in humid environments such as water reservoirs of air-conditioning systems. Because this fungal contaminant could be vaporized into the air and subsequently cause health problems, its monitoring is recommended. Currently, this monitoring is based on culture and microscopic identification which are complex, sometimes ambiguous and time-demanding, i.e., up to 21 days. Therefore, molecular, culture-independent methods could be more advantageous for the monitoring of E. jeanselmei. In this study, we developed a SYBR®green real-time PCR assay based on the internal transcribed spacer 2 from the 18S ribosomal DNA complex for the specific detection of E. jeanselmei. The selectivity (100 %), PCR efficiency (95.5 %), dynamic range and repeatability of this qPCR assay were subsequently evaluated. The limit of detection for this qPCR assay was determined to be 1 copy of genomic DNA of E. jeanselmei. Finally, water samples collected from cooling reservoirs were analyzed using this qPCR assay to deliver a proof of concept for the molecular detection of E. jeanselmei in environmental samples. The results obtained by molecular analysis were compared with those of classical methods (i.e., culture and microscopic identification) used in routine analysis and were 100 % matching. This comparison demonstrated that this SYBR®green qPCR assay can be used as a molecular alternative for monitoring and routine investigation of samples contaminated by E. jeanselmei, while eliminating the need for culturing and thereby considerably decreasing the required analysis time to 2 days.

ATR-FTIR Spectroscopy Highlights the Problem of Distinguishing Between Exophiala dermatitidis and E. phaeomuriformis Using MALDI-TOF MS

The present study compared two chemical-based methods, namely, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, to understand the misidentification of Exophiala dermatitidis and Exophiala phaeomuriformis. The study utilized 44 E. dermatitidis and 26 E. phaeomuriformis strains, which were partially treated with strong acids and bases for further evaluation. MALDI-TOF MS and ATR-FTIR spectroscopy data of the two Exophiala species were compared. Data groupings were observed for the chromic acid- and nitric acid-treated species when the black yeast sources were categorized as creosoted-oak sleepers, concrete sleepers, or dishwasher isolates. The MALDI-TOF MS data for the metalloenzyme-containing regions were consistent with the ATR-FTIR spectroscopy data. These results indicated that environmental isolates might contain metals not found in human isolates and might interfere with chemical-based identification methods. Therefore, MALDI-TOF MS reference libraries should be created for clinical strains and should exclude petroleum-associated environmental isolates.

Exophiala sideris, a novel black yeast isolated from environments polluted with toxic alkyl benzenes and arsenic

A novel species of the black yeast genus Exophiala (order Chaetothyriales) is described. Strains were repeatedly obtained by enriching samples of wild berries from different plants, guano-rich soil and from oak railway ties treated with arsenic creosote under a toluene-rich atmosphere. An identical strain was encountered in a closed arsenic mine polluted by alkyl benzenes. Its potential use for purposes of bioremediation is discussed.

Exophiala oligosperma involved in a refractory chronic rhinosinusitis

Fungal rhinosinusitis refers to a wide variety of conditions caused by fungal infections of the paranasal sinuses. Allergic fungal rhinosinusitis and sinus fungus balls are mostly noted in healthy individuals. Aspergillus species are supposed to be the most common etiologic agents of the disorder, but melanized fungi also occur, and these potentially are able to lead to fatal dissemination into brain parenchyma. We report on a case of fungus ball in a 20-year-old female with refractory chronic rhinosinusitis (RCRS) and bronchial asthma due to the black yeast Exophiala oligosperma which was confirmed by mycological and molecular (sequences of ITS rDNA) investigations. Exophiala oligosperma has previously not been reported to cause fungus balls or invasive fungal rhinosinusitis. Patient underwent functional endoscopic sinusitis surgery and the hypertrophic mucosa was removed completely. Without antifungal therapy, successful cure was achieved after spray therapy with corticosteroids for 1 month, without any relapse after a 6 month-follow up.

Bioproduction and anticancer activity of biosurfactant produced by the dematiaceous fungus Exophiala dermatitidis SK80

A new biosurfactant producer was isolated from palm-oilcontaminated soil and later identified through morphology and DNA sequencing as the yeast-like fungus Exophiala dermatitidis. Biosurfactant production was catalyzed by vegetable oil, supplemented with a basal medium. The culture conditions that provided the biosurfactant with the highest surface activity were found to be 5% palm oil with 0.08% NH4NO3, at a pH of 5.3, with shaking at 200 rpm, and a temperature of 30 degrees C for a 14-day period of incubation. The biosurfactant was purified, in accordance with surfactant properties, by solvent fractionation using silica gel column chromatography. The chemical structure of the strongest surface-active compound was elucidated through the use of NMR and mass spectroscopy, and noted to be monoolein, which then went on to demonstrate antiproliferative activity against cervical cancer (HeLa) and leukemia (U937) cell lines in a dose-dependent manner. Interestingly, no cytotoxicity was observed with normal cells even when high concentrations were used. Cell and DNA morphological changes, in both cancer cell lines, were observed to be cell shrinkage, membrane blebbling, and DNA fragmentation.

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.

New biosynthetic step in the melanin pathway of Wangiella (Exophiala) dermatitidis: evidence for 2-acetyl-1,3,6,8-Tetrahydroxynaphthalene as a novel precursor

The predominant cell wall melanin of Wangiella dermatitidis, a black fungal pathogen of humans, is synthesized from 1,8-dihydroxynaphthalene (D2HN). An early precursor, 1,3,6,8-tetrahydroxynaphthalene (T4HN), in the pathway leading to D2HN is reportedly produced directly as a pentaketide by an iterative type I polyketide synthase (PKS). In contrast, the bluish-green pigment in Aspergillus fumigatus is produced after the enzyme Ayg1p converts the PKS product, the heptaketide YWA1, to T4HN. Previously, we created a new melanin-deficient mutant of W. dermatitidis, WdBrm1, by random molecular insertion. From this strain, the altered gene WdYG1 was cloned by a marker rescue strategy and found to encode WdYg1p, an ortholog of Ayg1p. In the present study, two gene replacement mutants devoid of the complete WdYG1 gene were derived to eliminate the possibility that the phenotype of WdBrm1 was due to other mutations. Characterization of the new mutants showed that they were phenotypically identical to WdBrm1. Chemical analyses of mutant cultures demonstrated that melanin biosynthesis was blocked, resulting in the accumulation of 2-acetyl-1,3,6,8-tetrahydroxynaphthalene (AT4HN) and its oxidative product 3-acetylflaviolin in the culture media. When given to an albino W. dermatitidis strain with an inactivated WdPKS1 gene, AT4HN was mostly oxidized to 3-acetylflaviolin and deacetylated to flaviolin. Under reduced oxygen conditions, cell-free homogenates of the albino converted AT4HN to D2HN. This is the first report of evidence that the hexaketide AT4HN is a melanin precursor for T4HN in W. dermatitidis.

Spectrum of clinically relevant Exophiala species in the United States

Numerous members of the genus Exophiala are potential agents of human and animal mycoses. The majority of these infections are cutaneous and superficial, but also fatal systemic infections are known. We re-identified 188 clinical isolates from the United States, which had a preliminary morphological identification of Exophiala species, by sequencing internal transcribed spacer (ITS) region of the rRNA. Molecular identifications of the strains were as follows, in order of frequency: 55 E. dermatitidis (29.3%), 37 E. xenobiotica (19.7%), 35 E. oligosperma (18.6%), 13 E. lecanii-corni (6.9%), 12 E. phaeomuriformis (6.4%), 7 E. jeanselmei (3.7%), 7 E. bergeri (3.7%), 6 E. mesophila (3.2%), 5 E. spinifera (2.7%), 3 Exophiala sp. 1 (1.6%), 3 E. attenuata (1.6%), 3 Phialophora europaea (1.3%), 1 E. heteromorpha (0.5%), and 1 Exophiala sp. 2 (0.5%) strains. Exophiala strains were repeatedly isolated from deep infections (39.9%) involving lung, pleural fluid, sputum, digestive organs (stomach, intestines, bile), heart, brain, spleen, bone marrow, blood, dialysis fluid, lymph node, joint, breast, middle ear, throat, and intraocular tissues. About 38.3% of the Exophiala spp. strains were agents of cutaneous infections including skin, mucous membranes, nail, and corneal epithelium lesions. The other strains caused superficial infections (0.5%, including hair) or subcutaneous infection (12.0%, including paranasal sinusitis, mycetoma, and subcutaneous cyst). The systemic infections were preponderantly caused by E. dermatitidis, E. oligosperma, E. phaeomuriformis, E. xenobiotica, and E. lecanii-corni. Strains of E. bergeri, E. spinifera, E. jeanselmei, E. mesophila, and E. attenuata mainly induced cutaneous and subcutaneous infections. Since relatively few unknown ITS motifs were encountered, we suppose that the list of opportunistic Exophiala species in temperate climates is nearing completion, but a number of species still have to be described.

Exophiala crusticola anam. nov. (affinity Herpotrichiellaceae), a novel black yeast from biological soil crusts in the Western United States

A novel black yeast-like fungus,Exophiala crusticola, is described based on two closely related isolates from biological soil crust (BSC) samples collected on the Colorado Plateau (Utah) and in the Great Basin desert (Oregon), USA. Their morphology places them in the anamorphic genusExophiala, having affinities to the familyHerpotrichiellaceae(Ascomycota). Phylogenetic analysis of their D1/D2 large subunit nuclear ribosomal RNA (LSU nrRNA) gene sequences suggests that they represent a distinct species. The closest known putative relative toExophiala crusticolaisCapronia coronataSamuels, isolated from decorticated wood in Westland County, New Zealand. The holotype forExophiala crusticolaanam. nov. is UAMH 10686 and the type strain is CP141bT(=ATCC MYA-3639T=CBS 119970T=DSM 16793T). Dark-pigmented fungi appear to constitute an important heterotrophic component of soil crusts andExophiala crusticolarepresents the first description of a dematiaceous fungus isolated from BSCs.

Catheter-associated fungemia due to Exophiala oligosperma in a leukemic child and review of fungemia cases caused by Exophiala species

A case of catheter-associated fungemia due to Exophiala oligosperma in a 3-year-old leukemic child is presented. The etiologic agent was isolated from blood specimens and the catheter tip. The isolate was identified by its morphological characteristics and DNA sequencing of the internal transcribed spacer region of rDNA. Despite initial amphotericin B and itraconazole therapy, the child's fever subsided only after removal of the catheter. A review of the medical literature revealed 29 cases of infection due to Exophiala species. Twenty-three of these 29 patients had a CVC in place when they developed fever or other manifestations of fungemia. Withdrawal of the CVC together with amphotericin B and/or itraconazole therapy generally resulted in a good prognosis.

Intra-species variation of genotypes of Exophiala jeanselmei isolated from patients in Japan

Isolates of Exophiala jeanselmei have been classified into 15 types based on their mitochondrial DNA (mtDNA). Thirteen of the 15 types and E. spinifera, which has been classified as E. jeanselmei Type 14, were confirmed to be also clearly differentiated by restriction fragment length polymorphism (RFLP) in internal transcribed spacer (ITS) regions of ribosomal RNA genes in their nuclear DNA (nDNA). Twenty strains of E. jeanselmei, newly identified or isolated from patients in Japan, were examined for mtDNA-RFLP and ITS-RFLP. The twenty isolates were comprised of: 11 E. jeanselmei Type 5, 6 E. jeanselmei Type 6, 2 Type 10, and 1 Type 8. E. jeanselmei Type 6 was the second most common strain in Japan after Type 5. Type 5 was definitely identified as E. jeanselmei var. jeanselmei and Type 8 was identified as E. jeanselmei var. lecanii-corni based on the genotypes of type strains of these species. However, two other types were still designated as E. jeanselmei Type 6 and E. jeanselmei Type 10.

[Population studies of Exophiala jeanselmeis by sequence analysis in the ribosomal DNA]

OBJECTIVE

To study the populations of Exophiala jeanselmei strains from diverse sources using rDNA sequences.

METHODS

Tested strains included 20 isolates of Exophiala jeanselmei (type culture, reference culture, clinical and environmental isolates), 8 isolates of E. moniliae, 1 isolate of Exophiala werneckii, respectively. DNA was isolated with boiled-iced water method. Ribosomal DNA and its internal transcribed spacer regions were amplified and analyzed with sequencing.

RESULTS

The ribosomal genes of E. jeanselmei varied greatly. Twenty strains of this species were divided into 7 types. The genetic distances of some strains in this species were quite long.

CONCLUSION

The ribosomal RNA genes and their internal transcript sequences vary more widely than those of the other species in this genus.

Intestinal prevalence of the neurotropic black yeast Exophiala (Wangiella) dermatitidis in healthy and impaired individuals

A screening of 2300 samples of faeces from humans with and without underlying disease revealed that the black yeast Exophiala dermatitidis is present at a frequency of 5.2 per thousand (n=12). Eight individuals positive for the fungus had diarrhoea at the moment of its isolation, out of 11 where relevant information was available. Judging from repeated isolation over several weeks in one patient, the organism is able to persist in the human intestinal tract.

Identification of pathogenic dematiaceous fungi and related taxa based on large subunit ribosomal DNA D1/D2 domain sequence analysis

The nucleotide sequences of the D1/D2 domains of large subunit (26S) ribosomal DNA for 76 strains of 46 species of pathogenic dematiaceous fungi and related taxa were determined. Intra-species sequence diversity of medically important dematiaceous fungi including Phialophora verrucosa, Fonsecaea pedrosoi, Fonsecaea compacta, Cladophialophora carrionii, Cladophialophora bantiana, Exophiala dermatitidis, Exophiala jeanselmei, Exophiala spinifera, Exophiala moniliae, and Hortaea werneckii were extremely small; as few as 0 changes were detected in C. bantiana, Fonsecaea and Exophiala species, 1 bp in C. carrionii and H. werneckii, and 2 bp in P. verrucosa. Inter-species nucleotide diversity between most species was higher. These data suggested that the D1/D2 domain is sufficiently variable for identification of pathogenic dematiaceous fungi and relevant species. The phylogenetic trees constructed from the sequence data revealed that most human pathogenic species formed a single cluster and that Cladosporium and Phialophora species were distributed polyphyletically into several clusters.

Phaeohyphomycosis caused by Exophiala spinifera in India

The second case of phaeohyphomycosis due to Exophiala spinifera in India has been diagnosed 46 years after the initial case. The present case involved a 12-year-old female patient with no known immunocompromising conditions. She presented with multiple verrucous, well-defined plaques encompassing phaeohyphomycotic lesions of varying sizes on her face, chest, arms and thighs. Lymph node involvement in dissemination was confirmed by demonstrating pigmented fungal elements in histopathology of the left axillary node. The infection responded positively to prolonged administration of itraconazole. The original case involved a young boy and was similarly disseminated but was more severe, with bone involvement, and had a fatal outcome. It is likely that other such cases have occurred in the intervening time but have not been reported.

Species diversity and polymorphism in the Exophiala spinifera clade containing opportunistic black yeast-like fungi

A monophyletic group of black yeast-like fungi containing opportunistic pathogens around Exophiala spinifera is analyzed using sequences of the small-subunit (SSU) and internal transcribed spacer (ITS) domains of ribosomal DNA. The group contains yeast-like and annellidic species (anamorph genus Exophiala) in addition to sympodial taxa (anamorph genera Ramichloridium and Rhinocladiella). The new species Exophiala oligosperma, Ramichloridium basitonum, and Rhinocladiella similis are introduced and compared with their morphologically similar counterparts at larger phylogenetic distances outside the E. spinifera clade. Exophiala jeanselmei is redefined. New combinations are proposed in EXOPHIALA: Exophiala exophialae for Phaeococcomyces exophialae and Exophiala heteromorpha for E. jeanselmei var. heteromorpha.

Exophiala oligosperma causing olecranon bursitis

A 62-year-old male with a history of Wegener's granulomatosis and immunosuppressive therapy presented with chronic olecranon bursitis. A black velvety mould with brown septate hyphae and tapered annellides was isolated from a left elbow bursa aspirate and was identified as an Exophiala species. Internal transcribed sequence rRNA sequencing showed the isolate to be identical to Exophiala oligosperma. The patient was successfully treated with aspiration and intrabursal amphotericin B.

Identification of Exophiala mesophila isolated from treated dental unit waterlines

Members of the genus Exophiala are often difficult to identify to the species level because of their variable morphological appearances. This paper describes the methods used to identify Exophiala mesophila and provides salient differential features for distinguishing other mesophilic members of the genus.

Molecular diversity of oligotrophic and neurotropic members of the black yeast genus Exophiala, with accent on E. dermatitidis

Analysis of ITS rDNA of the black yeast Exophiala dermatitidis revealed a close phylogenetic relationship to the meristematic fungus Sarcinomyces phaeomuriformis. As most strains of S. phaeomuriformis have a yeast-like phenotype corresponding to the anamorph genus Exophiala, a new combination in Exophiala is proposed. On the basis of ITS sequence, M-13 fingerprint and SSU intron data, two main entities could be distinguished within E. dermatitidis. One of these (B) contained prevalently strains from environmental sources, while the other (A) mainly comprised strains from clinical sources. This may be due to a difference in virulence. All strains from severe brain and disseminated infections in East Asia clustered in group A. However, strains of group A caused a relatively mild fungemia in patients outside East Asia.

Specific oligonucleotide primers for identification of Hortaea werneckii, a causative agent of tinea nigra

Hortaea werneckii, a black yeast-like hyphomycete that is widely distributed in tropical and subtropical environments, can cause superficial mycotic infection in humans. This fungus was recently isolated from superficial infectious lesions of a guinea pig in Japan. An oligonucleotide primer set specific for Hortaea werneckii was designed on the basis of the internal transcribed spacer regions of the ribosomal DNA (rDNA). Polymerase chain reaction (PCR) with this primer set yielded a 306 bp PCR amplicon from only H. werneckii. This primer set did not amplify DNAs of 42 other related dematiaceous species, including the medically important dematiaceous fungi Cladophialophora carrionii, Fonsecaea pedrosoi, Phialophora verrucosa, and Exophiala dermatitidis, and eight species of medically important yeasts, including Candida (C.) albicans, C. dublinensis, C. glabrata, C. parapsilosis, C. tropicalis, Cryptococcus neoformans var. neoformans, Malassezia furfur, and Trichosporon asahii var. asahii. PCR with this primer set may be a useful technique for rapid identification of H. werneckii.

Molecular diversity, new species and antifungal susceptibilities in the Exophiala spinifera clade

Black yeasts morphologically identified as Exophiala cf. spinifera were re-analyzed on the basis of morphology, nutritional physiology and ITS rDNA sequencing data. Ribosomal small subunit (SSU) DNA sequence data confirmed that strains belonged to a clade containing the ex-type strain of E. spinifera. Variation in the Internal Transcribed Spacer (ITS) region of the rDNA was studied within this group. Five infraspecific groups were delineated. Phylogenetic analysis of the SSU rDNA data revealed that several of the strains analyzed were located at considerable evolutionary distance from the E. spinifera clade. ITS rDNA sequencing showed that the deviating strains could not be identified with any existing species. Two new species, E. attenuata and E. nishimurae, were therefore proposed. Antimycotic susceptibility data of the new species were compared with those obtained with members of the E spinifera clade.

Exopolysaccharides and capsules in human pathogenic Exophiala species

The black yeasts Exophiala spinifera and E. dermatitidis produce extracellular slimes, which may be either in the form of a well-delimited capsule or of diffusely exuded exopolysaccharides (EPS). The optimal conditions for their production were studied. The presence or absence of polysaccharide material can be used for recognition of the two species. Five-day-old cultures grown on potato glucose agar at 24 degrees C were observed in India ink, and positive identification for E. spinifera was obtained when significant halos were seen around yeast cells. In contrast, E. dermatitidis had irregular EPS with a fibrillar substructure made visible by alcian blue staining. Other Exophiala species produce insignificant amounts of extracellular mucus or none at all. The diagnostic method is particularly useful with yeast-like primary cultures, which often consist entirely of budding cells and lack the characteristic structures of the filamentous Exophiala synanamorph.

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

The black yeast Exophiala dermatitidis, an agent of fatal brain infections in East Asia, is common in European steam baths. The related fungi Sarcinomyces phaeomuriformis and Exophiala mesophila were isolated from locations in these complexes with lower ambient temperature and/or moisture. The latter two species had dry, rather than slimy, colonies and lower maximum growth temperatures (38 degrees C, 32 degrees C) than E. dermatitidis (42 degrees C). Exophiala dermatitidis produces abundant extracellular polysaccharide (EPS). The only E. dermatitidis strains lacking EPS were found outside the steam baths. Therefore it is likely that the extracellular polysaccharides commonly produced by E. dermatitidis are significant to survival under hot and moist conditions. Substrates sampled as controls, such as fruit surfaces and human faeces, yielded Exophiala dermatitidis at very low frequency.

Identification, classification, and phylogeny of the pathogenic species Exophiala jeanselmei and related species by mitochondrial cytochrome b gene analysis

We analyzed a 402-bp sequence of the mitochondrial cytochrome b gene of 34 strains of Exophiala jeanselmei and 16 strains representing 12 related species. The strains of E. jeanselmei were classified into 20 DNA types and 17 amino acid types. The differences between these strains were found in 1 to 60 nucleotides and 1 to 17 amino acids. On the basis of the identities and similarities of nucleotide and amino acid sequences, some strains were reidentified: i.e., two strains of E. jeanselmei var. hetermorpha and one strain of E. castellanii as E. dermatitidis (including the type strain), three strains of E. jeanselmei as E. jeanselmei var. lecanii-corni (including the type strain), three strains of E. jeanselmei as E. bergeri (including the type strain), seven strains of E. jeanselmei as E. pisciphila (including the type strain), seven strains of E. jeanselmei as E. jeanselmei var. jeanselmei (including the type strain), one strain of E. jeanselmei as Fonsecaea pedrosoi (including the type strain), and one strain of E. jeanselmei as E. spinifera (including the type strain). Some E. jeanselmei strains showed distinct nucleotide and amino acid sequences. The amino-acid-based UPGMA (unweighted pair group method with the arithmetic mean) tree exhibited nearly the same topology as those of the DNA-based trees obtained by neighbor joining, maximum parsimony, and maximum likelihood methods.

Nosocomial Exophiala jeanselmei pseudoinfection after sonography-guided aspiration of thoracic lesions

BACKGROUND AND PURPOSE

During the period from August 1994 to October 1998, a total of 19 isolates of Exophiala jeanselmei were recovered from 17 patients with various underlying thoracic diseases treated at National Taiwan University Hospital. The purpose of this study was to describe the clinical characteristics of these patients and to determine the microbiologic relatedness of the E. jeanselmei.

METHODS

Of the 19 isolates, 11 from nine patients were preserved and were identified based on their biotypes as determined by the API ID32C System, their cellular fatty acid profiles by gas-liquid chromatography, their antibiotypes to five antifungal agents by the E-test, and their random amplified polymorphic DNA (RAPD) patterns by arbitrarily primed PCR. Extensive environmental surveillance cultures and cultures from the skin of eight patients and hands of one physician were also performed.

RESULTS

One of the 17 patients had E. jeanselmei isolated from cutaneous phaeohyphomycosis (3 isolates), and the other 16 patients had isolations from pleural effusion specimens (15 isolates) or lung mass (1 isolate) following sonography-guided aspiration. The latter 16 patients had no clinical or pathologic evidence of fungal infection. Isolates (clone 1) from aspirated specimens had identical biotypes, antibiotypes, and RAPD patterns, which were different from those of the three isolates (clone 2) from the patient with a cutaneous lesion. All specimens from environmental sources, patients' skin, and the hands of the physician were negative for E. jeanselmei.

CONCLUSION

This series of patients demonstrates the difficulty in identifying the sources of a nosocomial pseudoinfection due to this slow-growing microorganism when isolated from pleural effusion specimens.

Mitochondrial DNA analysis of Exophiala jeanselmei var. lecanii-corni and Exophiala castellanii

A Japanese clinical isolate (KU-A-0094) which was identified by de Hoog et al. as Exophiala jeanselmei var. lecanii-corni with difficulty, was compared with 5 strains including the type cultures of E. jeanselmei var. lecanii-corni, var. jeanselmei and E. castellanii using RFLP (restriction fragment length polymorphism) patterns of mtDNA (mitochondrial DNA). RFLP patterns of KUA-0094 were identical with those of E. jeanselmei var. lecanii-corni and different from those of E. castellanii with restriction enzymes of HaeIII, MspI and hindIII. Therefore, de Hoog et al.'s identification of KU-A-0094 was confirmed. Additionally, mtDNA-RFLP patterns of E. jeanselmei var. lecanii-corni and E. jeanselmei var. jeanselmei were also different from each other. Consequently E. jeanselmei var. lecanii-corni seem to be a species in its own right rather than a variant of E. jeanselmei.

In vitro activities of five antifungal agents against pathogenic Exophiala species

OBJECTIVES

To examine the in vitro activities of five antifungal agents against common pathogenic Exophiala species; to detect the minimum inhibitory concentration (MIC) discrepancies among different drugs and different species; to evaluate the role of the influence factors in MIC determination; and to establish a standard method for the antifungal susceptibility testing of Exophiala spp.

METHODS

MICs of itraconazole (ICZ), fluconazole, ketoconazole, amphotericin B (AmB) and 5-flucytosine against 5 species (57 strains) of Exophiala spp were determined by modified NCCLS M27-A broth microdilution method. Two inoculum sizes (0.5 x 10(3)-2.5 x 10(3) CFU/ml and 0.5 x 10(4)-2.5 x 10(4) CFU/ml) and three incubation times (4, 7 and 10 days) were evaluated. The minimum fungicidal concentrations (MFC) of itraconazole against 20 Exophiala strains were also detected.

RESULTS

All the tested Exophiala species were sensitive to AmB and ICZ. MICs varied among different species and drugs. Resistant strains to different drugs existed in this genus. The proper inoculum density was about 0.5 x 10(3) CFU/ml to 2.5 x 10(3) CFU/ml, and the 4-day incubation time was suitable for more than 90% of the strains.

CONCLUSIONS

AmB or ICZ may serve as the first choice in treatment of phaeohyphomycosis. A standard microdilution procedure for MIC detection of Exophiala species is established in this experiment. The inoculum size and incubation time are the essential factors in the standardization of antifungal susceptibility testing of filamentous fungi. We hope this experiment may correlate well with the clinical treatment of phaeohyphomycosis caused by Exophiala species.

[A case of Exophiala dermatitidis ulceration]

The authors present one case of corneal Exophiala dermatitidis ulceration. This case is analyzed in the field of corneal mycosis infection. Classification, rate, clinical history, biomicroscopy aspects will be discussed. Technical samples will be described. Anatomopathologic slides will be discussed. Finally the medical or surgical treatment will be considered.

[Differentiation and characterization of yeasts pathogenic for humans (Candida albicans, Exophiala dermatitidis) and algae pathogenic for animals (Prototheca spp.) using Fourier transform infrared spectroscopy (FTIR) in comparison with conventional methods]

Due to the Fourier-Transform Infrared Spectroscopy (FT-IR) of strain specific traits demonstrated to be a suitable and efficient method for diagnostic and epidemiological determinations for the yeasts Candida albicans, Exophiala dermatitidis and the chlorophylless algae of the genus Prototheca. FT-IR leads in a rapid and economical way to reproducible results according to the spectral differences of intact cells (IR-fingerprints). Different genera, species and sub-species respectively, different strains can be recognized and grouped into different clusters and subclusters. The FT-IR analysis of Candida albicans isolates (n = 150) of 22 newborns-at-risk of an intensive care unit showed, that 86% of the children were colonised with several (2-4) different strains in the oral cavities and faeces. Stationary cross-infections could definitely be determined. Exophiala dermatitidis isolates (n = 31), mostly isolated repetitively within a period of 3 years from sputa of patients suffering from cystic fibrosis could be characterized and grouped patient-specifically over the total sampling period. Of 6 from 8 patients (75%) their individual strains remain the same and could be tracked over the three years. Cross-infections during the stationary treatment could be clearly identified by FT-IR. The Prototheca isolate (n = 43) from live-stock and farm environment showed clear distinguishable clusters differentiating the species P. wickerhamii, P. zopfii and P. stagnora. In addition, the biotypes of P. zopfii could be distinguished, especially the subclusters of variants II and III. It could be demonstrated, that FT-IR is suitable for the routine identification and differentiation of yeasts and algae. However, in spite of the gain of knowledge by using FT-IR for the characterization of microorganisms, the conventional phenotyping and/or genetic analysis of yeast or algae strains cannot be replaced completely. For a final taxonomic classification a combination of conventional methods on FT-IR together with more sophisticated molecular genetic procedures is necessary.

Exophiala dermatitidis and Sarcinomyces phaeomuriformis: ITS1-sequencing and nutritional physiology

The internal transcribed spacer 1 (ITS1) sequences of the nuclear rRNA gene (approximately 200 bp) of 33 strains of the Exophiala dermatitidis complex were determined; two similar species were added for comparison. A core group (I), including the type strain CBS 207. 35, contained 20 identical strains which had previously been found to have introns in their small sub-unit (SSU) rDNA. Eleven remaining strains identified as E. dermatitidis (groups II-V) differed from the core group in 1-4 nucleotide positions (plus a deletion in one strain); most of them lacked introns in their SSU ribosomal genes. The type strain of the meristematic species Sarcinomyces phaeomuriformis CBS 131.88 was found to differ significantly from E. dermatitidis. One strain had the annellidic morphology of E. dermatitidis, but the ITS1 sequence of S. phaeomuriformis. Strain CBS 709.95, an E. dermatitidis reported to have a meristematic synanamorph, was found to have ITS1 identity to the type strain of E. dermatitidis, although SSU sequences established previously suggested a close relationship with S. phaeomuriformis. Slight physiological differences were found between E. dermatitidis and S. phaeomuriformis. An oligonucleotide probe specific for E. dermatitidis was designed, thus able to discriminate this species from closely related black yeasts.

A comparison of methods of phenotypic and genotypic fingerprinting of Exophiala dermatitidis isolated from sputum samples of patients with cystic fibrosis

Phenotypic and genotypic characteristics of 11 strains of Exophiala dermatitidis were investigated. Ten strains (including three reference strains) were isolated from sputum samples of six patients with cystic fibrosis (CF) in Germany, and one reference strain was isolated from a patient with phaeohyphomycosis in Japan. The strains showed differences in their ability to assimilate sorbitol, palatinose, rhamnose, gluconate and melezitose, leading to the differentiation of seven auxotypes. The IC30 of amphotericin B, and ketoconazole and itraconazole, respectively, indicated susceptibility, whereas the IC30 of fluconazole and 5-fluorocytosine indicated resistance in all strains. Protein patterns in SDS-PAGE revealed no major differences. The glycoconjugate patterns distinguished the Japanese strain from the other strains. Cluster analysis of whole-cell fatty acid methyl ester (FAME) profiles with the Microbial Identification System (MIS) revealed two major clusters separating a reference strain and the Japanese strain from the other strains. Analysis of patterns resulting from random amplification of polymorphic DNA (RAPD) with two arbitrary primers showed four genotypes. Comparison of the results revealed no agreement between the different fingerprinting methods, except the separation of the Japanese strain from the European CF strains. As the results of assimilation tests seem to vary between different laboratories, the analysis of FAME profiles and RAPD analysis are recommended for typing E. dermatitidis.

Identification of dematiaceous fungi and their role in human disease

Phaeohyphomycosis is the disease caused by the dematiaceous hyphomycetes or those fungi that are darkly pigmented because of the presence of melanin in their cell wall. Infections with these fungi may remain localized at the site of traumatic inoculation or within the sinuses or may become disseminated. As these fungi pose a significant problem to both the clinician who must treat the patient and the laboratorian faced with identification of the organism, a selection of representative organisms was presented at the meeting entitled "Focus on Fungus Infections." These fungi often infect patients who are not overtly immunocompromised and therefore may be encountered in a wide variety of cases.

Exophiala mesophila spec. nov

In this paper a new fungus species, Exophiala mesophila Listemann et Freiesleben, is described. The species was isolated from silicone seals in the shower room of a hospital ward.

A human isolate of Exophiala (Wangiella) dermatitidis forming a catenate synanamorph that links the genera Exophiala and Cladophialophora

A strain of the black yeast Exophiala dermatitidis displayed a hydrophobic synanamorph consisting of acropetal chains of lemon-shaped conidia, morphologically similar to those of Cladophialophora bantiana. The occurrence of the two conidial types in a single strain suggests a taxonomic affinity between Exophiala and Cladophialophora and provides support to the supposition that Cladophialophora, a possible anamorph genus of Herpotrichiellaceae, is related to black yeasts rather than to Cladosporium, which has teleomorphs in the Mycosphaerellaceae.

Phylogenetic analysis of ten black yeast species using nuclear small subunit rRNA gene sequences

The nuclear small subunit rRNA genes of authentic strains of the black yeasts Exophiala dermatitidis, Wangiella dermatitidis, Sarcinomyces phaemuriformis, Capronia mansonii, Nadsoniella nigra var. hesuelica, Phaeoannellomyces elegans, Phaeococcomyces exophialae, Exophiala jeanselmei var. jeanselmei and E. castellanii were amplified by PCR and directly sequenced. A putative secondary structure of the nuclear small subunit rRNA of Exophiala dermatitidis was predicted from the sequence data. Alignment with corresponding sequences from Neurospora crassa and Aureobasidium pullulans was performed and a phylogenetic tree was constructed using the neighbor-joining method. The obtained topology of the tree was confirmed by bootstrap analysis. Based upon this analysis all fungi studied formed a well-supported monophyletic group clustering as a sister group to one group of the Plectomycetes (Trichocomaceae and Onygenales). The analysis confirmed the close relationship postulated between Exophiala dermatitidis, Wangiella dermatitidis and Sarcinomyces phaeomuriformis. This monophyletic clade also contains the telemorph species Capronia mansonii thus confirming the concept of a teleomorph connection of the genus Exophiala to a member of the herpotrichiellaceae. However, Exophiala castellanii did not belong to this clade. Therefore, this species is not the anamorph of Capronia mansonii as it was postulated.

Nutritional physiology of type isolates of currently accepted species of Exophiala and Phaeococcomyces

Nutritional physiological and tolerance tests were performed for all type strains of species currently classified in the black yeast genera Exophiala and Phaeococcomyces, including some additional type strains of taxa recently reidentified as Exophiala species. Most described Exophiala species can be distinguished by physiological characters. Exophiala jeanselmei with its varieties, and E. castellanii should all be retained as separate taxa. The pairs of strains Mycotorula schawii/Exophiala dermatitidis, Hormodendrum negronii/Exophiala jeanselmei var. lecaniicorni and Sporotrichum gougerotii/Torulabergeri were found to be conspecific. Phenetic analyses of physiological data support the identity of Phaeococcomyces exophialae as a yeast-like synanamorph of Exophiala spinifera. The taxonomic positions of the genera Nadsoniella, Phaeoannellomyces and Wangiella are discussed. The genera Exophiala and Phaeococcomyces are unrelated.

PCR-ribotyping of type isolates of currently accepted Exophiala and Phaeococcomyces species

Portion of the ribosomal repeat of the type strains of the genera Exophiala and Phaeococcomyces were subjected to RFLP analysis. The amplicon length of the small subunit rRNA, the fragment NS1-NS24, was found to vary between 1800 to 3200 nucleotides. In contrast, the length of the fragment ITS1-ITS4 comprising the internal transcribed spacers (ITS1 and ITS2) was found to be constant at 600 nucleotides. Analysis of restriction profiles confirmed the synonymy of Exophiala dermatitidis and Mycotorula schawaii. Torula bergeri and Sporotrichum gougerotii were found to be identical to Phaeoannellomyces elegans, but different from their alleged synonym E. castellanii. A phenogram is presented.

Pathogenicity of strains of the black yeast Exophiala (Wangiella) dermatitidis: an evaluation based on polymerase chain reaction

Strains of Exophiala dermatitidis, mainly originating from patients with systemic neurotropic mycosis in Asia and from the lungs of patients with cystic fibrosis (CF) in Europe, were analysed by ribotyping of the small subunit rDNA and by random amplification of polymorphic DNA (RAPD). A characteristic banding pattern for the species was found after restriction analysis of amplified fragments V9 and ITS4. The small subunit rDNA gene of five strains was about 1800 base pairs (bp) long, while in 16 strains its length was about 3000 bp. Using RAPD, seven populations could be distinguished. European CF strains as well as Asian strains from systemic mycoses are mainly distributed over two populations, one of which contained both CF strains and a systemic strain. It is concluded that the two clinical pictures are caused by genetically similar strains. The differences in pathogenicity may be explained by immunological differences in the hosts or by differences in exposure to the fungal propagules.

Clinical and mycological spectra of Wangiella dermatitidis infections

The article reviews 37 cases of phaeohyphomycosis from the world literature up to 1992 accepted as being caused by Wangiella dermatitidis. The various clinical aspects of these infections are characterized, and the nomenclatural implications in the history of this emerging pathogen are discussed.

Mitochondrial DNA analysis of Exophiala moniliae

Mitochondrial DNA (mtDNA) analysis with restriction enzymes, Hae III, Hind III and Msp I was performed in 17 Exophiala moniliae strains. The results were as follows: (1) E. moniliae could be classified into 10 types based on restriction patterns, (2) E. moniliae is suggested to be a complex organism because of extensive mtDNA polymorphism among strains like E. jeanselmei and (3) two types of E. moniliae are identical with two types of E. jeanselmei. These results suggest that E. moniliae is not genetically defined from E. jeanselmei and the taxonomical status of E. moniliae requires reevaluation.

Karyology and hyphal characters as taxonomic criteria in ascomycetous black yeasts and related fungi

Mycelial development of seventy-three strains of black yeasts and related fungi were studied, and numbers of nuclei per hyphal cell were counted. Two main patterns were apparent in expanding hyphae, viz. (1) uninucleate expanding hyphal cells, septum formation strictly following mitosis, and (2) multinucleate, branched, aseptate hyphal tips, septa being formed in a later stage, leading to oligo- or uninucleate mature cells. Characteristic genera in the two groups are Exophiala and Aureobasidium, respectively. In Zasmidium and in some Ramichloridium species all mycelial cells are oligonucleate. The character is indicative for relationships at the family level in black yeasts.

Mitochondrial DNA analysis of Exophiala jeanselmei and Exophiala dermatitidis

Mitochondrial DNA (mtDNA) analysis with Hae III, Hind III and Msp I was performed in 45 Exophiala jeanselmei strains (30 Phialophora jeanselmei and 154 Phialophora gougerotii strains) and 31 Exophiala dermatitidis strains. The results were as follows, 1) P. jeanselmei and P. gougerotii are identical, 2) E. jeanselmei is classified into 18 types based on restriction profiles, 3) two strains of E. jeanselmei CBS 577.76 and CBS 578.76 are identified as E. dermatitidis, 4) E. dermatitidis has no intraspecific variation and is definitely distinct from E. jeanselmei, 5) E. jeanselmei is suggested to be a complex organism because of extensive mtDNA polymorphism.

Evaluation of the API 20C yeast identification system for the differentiation of some dematiaceous fungi

Ninety-seven isolates of Cladosporium spp., Exophiala spp., Fonsecaea spp., Lecythophora hoffmannii, Phaeoannellomyces werneckii, Phialophora spp., Wangiella dermatitidis, and Xylohypha bantiana were used to evaluate the API 20C Yeast Identification System for the differentiation of dematiaceous fungi. Using the API 20C system, we were able to distinguish most species of Phialophora and Cladosporium and to separate L. hoffmannii from the species of Phialophora tested; X. bantiana from C. carrionii, C. resinae, and C. sphaerospermum; and W. dermatitidis from Exophiala jeanselmei and Exophiala spinifera. Ninety-two (60.1%) of 153 possible species-pair combinations were separated.

Deoxyribonucleic acid hybridization studies of Exophiala dermatitidis and Exophiala jeanselmei

Exophiala dermatitidis and Exophiala jeanselmei share similar morphological features and have been confused with each other. To clarify the relationship between the two fungi, we conducted a deoxyribonucleic acid (DNA)-DNA hybridization study using a dot blot method. Between E. dermatitidis and E. jeanselmei, only a very low level of DNA relatedness was seen and it was confirmed that these two fungi are distinct species based on DNA similarity. Close correspondence of DNA from the isolates of E. dermatitidis was obtained, whereas the isolates of E. jeanselmei were divided into 6 groups according to their DNA similarity and a possibility was shown that E. jeanselmei is composed of genetically heterogeneous groups. The subdivision of the species E. jeanselmei by the DNA-DNA hybridization method was in agreement with serotyping exoantigens. This result suggests that DNA-DNA hybridization studies provide an excellent tool for the identification and grouping of pathogenic dematiaceous fungi.

Evaluation of proteolytic activity to differentiate some dematiaceous fungi

A total of 123 isolates of Cladosporium spp., Exophiala spp., Fonsecaea spp., Lecythophora hoffmannii, Phaeoannellomyces werneckii, Phialophora spp., Wangiella dermatitidis, and Xylohypha bantiana were tested for proteolytic activity by using 26 different formulations of gelatin, milk, casein, and Loeffler media. Other physiological properties examined included hydrolysis of tyrosine and xanthine, sodium nitrate utilization in Czapek Dox agar, and thermotolerance. Isolates of Exophiala jeanselmei, Fonsecaea compacta, Fonsecaea pedrosoi, W. dermatitidis, and X. bantiana lacked proteolytic activity. Proteolytic activity was variable among the remaining species, depending on the type of medium used. Thermotolerance had value in distinguishing some taxa.

[First isolation of Exophiala jeanselmei (Lang) De Hoog from a dental granuloma]

Exophiala jeanselmei (Lang) De Hoog was isolated from a granuloma of a dental decay. Its systematic position and morphology in optical microscopy are widely discussed in accordance with current views.