S. de Hoog

Dermatophytes: recognizing species of clonal fungi

Now that molecular data have forever changed our perspective on the anthropophilic and zoophilic dermatophyte species, the concepts of these species needs re-evaluation. In this paper, main concepts (morphological, biological (BSC), phylogenetic and genealogical concordance phylogenetic species recognition (GCPSR)) are compared. While in geophilic dermatophytes the application of the BSC works well for species distinction and is supported by molecular data, it is not applicable for the anthropophilic and zoophilic dermatophytes where the majority of species reproduce purely asexually. Also, the application of GCPSR (an operational method to define the limits of species using molecular, multi-locus data) is problematic. GCPSR can be applied in recombining fungi even when recombination is infrequent and fungi lack phenotypic sexuality. In truly clonal fungi, however, no incongruities in multi-locus data are found, and thus separation of species may be difficult. In fungi this problem is currently taken to be non-existent, since clonality is supposed to lead to extinction. In the medically relevant, host-associated dermatophytes, however, is reason to suggest that clonal dermatophyte lineages are able to maintain ongoing populations and to follow independent evolutionary trajectories. We distinguish seasonal, short-lived and long-lived clonal species. The final goal of a species concept, in the dermatophytes as well as in other fungi, is to provide a taxonomic system that reflects the evolution of the fungal species so that the underlying biological trends elucidated in this way may be brought forward to help to guide the clinician in applying optimal therapy and prophylaxis. The application of the different species concepts may have an enormous impact on the nomenclature of dermatophytes, directly affecting the quality of communications with care providers.

Origins of Microsatellite Diversity in the Trichophyton rubrum- T. violaceum Clade (Dermatophytes)

ABSTRACT We analyzed the population structure of the anthropophilic dermatophyte species Trichophyton violaceum, which mainly causes tinea capitis, and T. rubrum, the most frequently isolated agent of dermatophytosis worldwide. A microsatellite marker (T1) was developed by using the enrichment technique for microsatellites. The T1 marker containing a (GT)8-10 repeat was proven to specifically amplify both species, underlining their close kinship. Four polymorphic alleles were detected within a set of about 130 strains by using polyacrylamide gel electrophoresis with this marker. An association with geographic origin of the isolates was apparent. Given the close relatedness of both species, these data suggest an African origin of the entire T. rubrum complex, followed by the emergence of a new genotype (B) in Asia with subsequent spread of this genotype over Europe and the United States.

Diversity of Bipolaris Species in Clinical Samples in the United States and Their Antifungal Susceptibility Profiles

ABSTRACT A set of 104 isolates from human clinical samples from the United States, morphologically compatible with Bipolaris, were morphologically and molecularly identified through the sequence analysis of the internal transcribed space (ITS) region of the nuclear ribosomal DNA (rDNA). The predominant species was Bipolaris spicifera (67.3%), followed by B. hawaiiensis (18.2%), B. cynodontis (8.6%), B. micropus (2.9%), B. australiensis (2%), and B. setariae (1%). Bipolaris cynodontis, B. micropus, and B. setariae represent new records from clinical samples. The most common anatomical sites where isolates were recovered were the nasal region (30.7%), skin (19.2%), lungs (14.4%), and eyes (12.5%). The antifungal susceptibilities of 5 species of Bipolaris to 9 drugs are provided. With the exception of fluconazole and flucytosine, the antifungals tested showed good activity.

Case Report. Atypical cutaneous pseudallescheriosis refractory to antifungal agents

We report on a 65‐year‐old male heart transplant recipient who was otherwise in good condition. The patient was immunocompromised secondarily due to cyclosporin, prednisolone and azathioprine when widespread pustular skin lesions with erythematous margins subsequently developed on his left forearm. There was no history of trauma or septic temperature. Bacterial cultures were sterile and the results of native and cultural investigation studies were negative. A biopsy specimen of the lesion demonstrated hyalohyphomycosis with numerous septate hyphae within granulomas throughout the dermis. Subcutaneous tissues were not involved. Culture plates inoculated with pus and skin from the punch biopsy showed growth of a mould yielding Pseudallescheria boydii. Sensitivity testing was performed with miconazole, ketoconazole and itraconazole showing the best in vitro activity against P. boydii. In spite of treatment with itraconazole, the erythema and pustules continued to spread and therapy was changed to intravenous miconazole. Due to ongoing progression after 3 months of antifungal therapy surgical debridement was required. After 2 years of follow up, he had no recurrence.

Survival of a neglected case of brain abscess caused by Cladophialophora bantiana

Cladophialophora bantiana is an uncommon fungus related to the black yeasts which causes, if untreated, mostly fatal cerebral infections in immunosuppressed and competent patients. We report a case of a patient who survived a recurrent cerebral abscess caused by C. bantiana despite delayed and apparently inappropriate therapy.