Impact of conidiogenesis, teleomorph connections, pleomorphism and molecular genetics on evolving hyphomycete systematics

Adiaspiromycosis causing respiratory failure and a review of human infections due to Emmonsia and Chrysosporium spp

We report a case of a 27-year-old male who presented with respiratory distress that required mechanical ventilation. Transbronchial biopsy revealed adiaspores of the fungus Emmonsia crescens within granulomata, a condition known as adiaspiromycosis. The patient received amphotericin products and corticosteroids, followed by itraconazole, and made a full recovery. Emmonsia crescens is a saprobe with a wide distribution that is primarily a rodent pathogen. The clinical characteristics of the 20 cases of human pulmonary adiaspiromycosis reported since the last comprehensive case review in 1993 are described here, as well as other infections recently reported for the genus Emmonsia. Pulmonary adiaspiromycosis has been reported primarily in persons without underlying host factors and has a mild to severe course. It remains uncertain if the optimal management of severe pulmonary adiaspiromycosis is supportive or if should consist of antifungal treatment, corticosteroids, or a combination of the latter two. The classification of fungi currently in the genus Emmonsia has undergone considerable revision since their original description, including being grouped with the genus Chrysosporium at one time. Molecular genetics has clearly differentiated the genus Emmonsia from the Chrysosporium species. Nevertheless, there has been a persistent confusion in the literature regarding the clinical presentation of infection with fungi of these two genera; to clarify this matter, the reported cases of invasive Chrysosporium infections were reviewed. Invasive Chrysosporium infections typically occur in impaired hosts and can have a fatal course. Based on limited in vitro susceptibility data for Chrysosporium zonatum, amphotericin B is the most active drug, itraconazole susceptibility is strain-dependent, and fluconazole and 5-fluorocytosine are not active.

Dematiaceous fungal pathogens: analysis of ribosomal DNA gene polymorphism by polymerase chain reaction-restriction fragment length polymorphism

Restriction fragment length polymorphisms (RFLP) of ribosomal gene small subunit (SSU rDNA) and internal transcribed spacer (ITS) regions was examined in 12 isolates of dematiaceous agents of chromoblastomycosis and phaeohyphomycosis. The amplicon length of the fragment ITS1-ITS4, comprising the 5.8 rDNA and ITS1-ITS2 spacers, ranged in size from 620 to 690 bp. This result indicated a polymorphism of size in this region. Additionally the RFLP profiles showed a high degree of inter- and intra-specific variability. In contrast, the SSU rDNA amplification, using NS1-NS2 primers, originated a fragment of approximately 570 bp and its restriction profile proved to be well conserved among the species studied and was clustered into only two genetically heterogeneous groups, the first one formed by Fonsecaea pedrosoi and Fonsecaea compacta and the second one formed by Cladophialophora (Cladosporium) carrionii, Cladophialophora (Xylohypha) bantiana, Phialophora verrucosa and Rhinocladiella species.

Use of RAPD (random amplified polymorphic DNA) to analyse genetic diversity of dematiaceous fungal pathogens

Thirteen strains of chromoblastomycosis and phaeohyphomycosis etiologic agent fungi were obtained from different geographical origins. These strains were genotypically compared by means of the RAPD (Random Amplified Polymorphic DNA) technique. The data generated showed a high degree of polymorphism between distinct species and a low polymorphism between strains of the same species. The results generated by these tests were subjected to a numerical taxonomy analysis, using the unweighted pair-group method. A phenogram was constructed for the set of strains studied. Based on its structure, we concluded that genotypical data provide enough information to us to use the unweighted pair-group method to cluster the strains in accordance to their respective species. The phenogram grouped in a single branch the strains of Fonsecaea pedrosoi and F. compacta species, indicating a great similarity between these fungi, and suggesting that the classification as distinct species may not be appropriate for these species of the genus Fonsecaea.Key words: chromoblastomycosis, phaeohyphomycosis, dematiaceous fungi, RAPD,Fonsecaea pedrosoi.

Molecular genetic variation in Emmonsia crescens and Emmonsia parva, etiologic agents of adiaspiromycosis, and their phylogenetic relationship to Blastomyces dermatitidis (Ajellomyces dermatitidis) and other systemic fungal pathogens

Emmonsia crescens, an agent of adiaspiromycosis, Blastomyces dermatitidis, the agent of blastomycosis, and Histoplasma capsulatum, the agent of histoplasmosis, are known to form meiotic (sexual) stages in the ascomycete genus Ajellomyces (Onygenaceae, Onygenales), but no sexual stage is known for E. parva, the type species of the genus Emmonsia. To evaluate relationships among members of the putative Ajellomyces clade, large-subunit ribosomal and internal transcribed spacer region DNA sequences were determined from PCR-amplified DNA fragments. Sequences were analyzed phylogenetically to evaluate the genetic variation within the genus Emmonsia and evolutionary relationships to other taxa. E. crescens and E. parva are distinct species. E. crescens isolates are placed into two groups that correlate with their continents of origin. Considerable variation occurred among isolates previously classified as E. parva. Most isolates are placed into two closely related groups, but the remaining isolates, including some from human sources, are phylogenetically distinct and represent undescribed species. Strains of B. dermatitidis are a sister species of E. parva. Paracoccidioides brasiliensis and Histoplasma capsulatum are ancestral to most Emmonsia isolates, and P. brasiliensis, which has no known teleomorph, falls within the Ajellomyces clade.

The genus Uncinocarpus (Onygenaceae) and its synonym Brunneospora: new concepts, combinations and connections to anamorphs in Chrysosporium, and further evidence of relationship with Coccidioides immitis

The genus Uncinocarpus (Onygenales, Onygenaceae) is emended to include keratinophilic fungi with discrete, globose gymnothecial ascomata without differentiated ascomatal hyphae and bearing uncinate, helical, or no appendages; oblate, punctate ascospores sometimes with irregular reticulations; bulbous initials, and Malbranchea or Chrysosporium anamorphs. The new combination Uncinocarpus orissi is proposed for Pseudoarachniotus orissi; Gymnoascus arxii is shown to be a synonym. New records show that the fungus has a wide distribution from North America, Europe, Asia, and the Middle East. The teleomorph is formed under laboratory conditions by mating representative isolates. The anamorph has been described under the names Chrysosporium zonatum and Chrysosporium gourii. Chrysosporium queenslandicum is morphologically similar. Its teleomorph Apinisia queenslandica is transferred also to the genus Uncinocarpus as Uncinocarpus queenslandicus. Brunneospora reticulata, the type species of the genus Brunneospora, is a synonym. Orromyces spiralis appears to be another name applied to this fungus. Development of helical coils in an isolate of Coccidioides immitis provides further evidence of a possible relationship between this dimorphic human pathogen and this group of ascomycetes.Key words: Uncinocarpus, Onygenales, systematics, keratinophiles, human pathogen.

Molecular taxonomy and epidemiology of Blastomyces and Histoplasma species

Cladistic analysis of partial 26S rRNA sequences was used to estimate evolutionary distances among species and varieties of the dimorphic onygenalean genera Blastomyces, Coccidioides, Emmonsia, Histoplasma and Paracoccidioides. With the exception of Coccidioides, all genera were closely related, with about 5% base differences and even less (1-2%) between Blastomyces and Emmonsia. These data were supported by a teleomorph in the same genus Ajellomyces. In a phylogenic study of a wide range of ascomycete orders and families, Coccidioides immitis was found to be closest to Aphanoascus fulvescens and Chrysosporium keratinophilum, and to have relative distances to the remaining dimorphic genera (family Onygenaceae) similar to those of the dermatophytes (family Arthrodermataceae). The sequencing data were confirmed by genomic comparisons. All dimorphic genera had a nuclear DNA base composition in the same range of 46.6-47.3% G + C. The DNA melting curves of Blastomyces and Histoplasma strains showed irregularities that were ascribed to the presence of AT-rich stretches in satellite DNA rather than in mitochondrial DNA. Derivative profiles proved to be highly reproducible within regional populations and coincided with differences in clinical behaviour of each species. Blastomyces dermatitidis generated two kinds of curves, corresponding to the geographically distinct serotypes 1 and 2. The African type (serotype 2) was characterized by a classical sigmoidal melting curve similar to that for all strains of Coccidioides, Emmonsia and Paracoccidioides. In contrast, the American type (serotype 1) contained satellite DNA (27% G + C). A rRNA base difference of 1.5% was observed between geographical types, a value slightly higher than that noted between Histoplasma capsulatum and its variety farciminosum (0.9%). All three H. capsulatum varieties presented irregularities in their DNA melting curves. The molecular data support the recognition of two of them as agents of blastomycosis and the assignment of more than one species and two varieties to the genus Emmonsia.

Pulmonary adiaspiromycosis in a two year old girl

A case of disseminated bilateral pulmonary adiaspiromycosis is reported in a two year old Finnish girl. She recovered from this rare infection after treatment with amphotericin B. She is the first human case of adiaspiromycosis in Scandinavia and she is the youngest child with this disease reported so far. Electron microscopy showed that the three layers of the spore wall were not typical; rather, there seemed to be a gradual transition between the main wall zones, which may be split into an indefinite number of thin layers. Varying numbers and thicknesses were seen with different staining methods, and in different spores. Diagnosis relies on recognition of the fungus in a pulmonary biopsy specimen, because there are no reliable serological tests and culture of the fungus is time consuming and not always successful. It was thought that this patient had become infected as a result of contact with soil dust containing the spores in the yard surrounding her home, and as a result of her mother's work in a large garden shop.

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.

Polymerase chain reaction-based detection of dermatophyte DNA with a fungus-specific primer system

There is significant clinical interest in primers which are specific for fungi and do not hybridize to DNA of other eukaryotes or prokaryotes. Such primers would allow specific amplification of fungal DNA from human tissue samples containing fungi. Fungal identification to the species level could follow by direct sequencing or restriction analysis. Several previously described primer systems cross-react with DNA of plants and animals. We have designed a primer system that amplifies a fragment of the gene coding for the small ribosomal subunit 18S rRNA. Database searches and sequence analyses were performed using the HUSAR (Heidelberg Unix Sequence Analysis Resources) computer system at the German Cancer Research Centre, Heidelberg, Germany. Primers TR1 (5'-GTTTCTAGGACCGCCGTA) and TR2 (5'-CTCAAACTTCCATCGACTTG) bind to sequences which are homologous within the fungi, but differ from corresponding DNA fragments of plants and animals. The amplified fragment is 581 base pairs in length and contains variable, and therefore species-specific, regions. The DNA of Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton verrucosum, Trichophyton terrestre, Microsporum canis, Microsporum gypseum and Epidermophyton floccosum and of several yeast species was amplified by the primers, but not the DNA from 42 normal human skin samples. Furthermore, other DNA preparations from plants and animals, including those from radish, cabbage, wheat and mouse, did not show amplification reactions.

Rapid presumptive identification of medically relevant yeasts to the species level by polymerase chain reaction and restriction enzyme analysis

A method for the rapid presumptive differentiation of a panel of 12 clinically relevant yeasts to the species level was developed on the basis of evaluation by the polymerase chain reaction (PCR) of the gene coding for the small ribosomal subunit 18S-rRNA. The method involved restriction enzyme analysis of PCR products obtained with primers common to all fungi. Using six restriction enzymes, AluI, BanI, BbsI, DraII, Eco147I and NheI, characteristic PCR-restriction enzyme patterns were obtained for Candida albicans, Candida tropicalis, Candida krusei, Candida kefyr, Candida lusitaniae, Candida guilliermondii, Candida glabrata and Saccharomyces cerevisiae, as well as for the pairs Candida parapsilosis/Candida viswanathii and Trichosporon beigelii/Cryptococcus neoformans. The procedure does not involve hybridization steps or the use of radioactivity and can be completed within one working day.

Phylogeny of dermatophytes and dimorphic fungi based on large subunit ribosomal RNA sequence comparisons

The phylogeny of dermatophytes and dimorphic fungi was considered using the large-subunit of ribosomal RNA (25S rRNA). Aligned sequences of 595 nucleotides covering the two most divergent domains D1 and D2, permitted a comparison of phylogenetic relationships at different levels. The dimorphic species (Onygenaceae) were significantly separated from dermatophytes (Arthrodermataceae) and from a third group including geophilic or very weakly pathogenic species (Onygenaceae and Gymnoascaceae). On a species level, the varietal status of Histoplasma duboisii and Histoplasma farciminosum, as close relations of Histoplasma capsulatum, was confirmed. The dimorphic fungus Emmonsia parva, in spite of a completely different parasitic form (adiaspores instead of yeast-like cells), clustered with Blastomyces dermatitidis which has a perfect form resembling that of H. capsulatum. From our data, teleomorphs of E. parva, Paracoccidioides brasiliensis and H. farciminosum, three dimorphic fungi known only under their anamorphic states, should belong to the family of Onygenaceae and the genus Ajellomyces. Among Arthrodermataceae, and family containing the most keratinophilic species, it was not possible to establish a clear hierarchy of species. Only Ctenomyces serratus, the species adapted to degrade keratin of feathers, Trichophyton ajelloi and Trichophyton terrestre were significantly separated. The speciation of true dermatophytes resulted most likely from a very recent evolution by adaptation to parasitism. Among species used as outgroups, the two emerging pathogens Pseudallescheria boydii (Scedosporium apiospermum) and Scedosporium prolificans (Scedosporium inflatum) were shown to be closely related to each other.