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.