Wangiella (Exophiala) dermatitidis. Wangiella dermatitidis is a black (melanized) fungus that is recognized as a paradigm for the emerging human mycosis known as phaeohyphomycosis and also as a model for the more than one hundred other black fungi known to cause human disease.[1,2,3] Since its first isolation in Japan in 1937 and its description as a skin pathogen, Wangiella has been assigned to numerous Fungi Imperfecti genera, is known to have a world-wide distribution, and has been isolated from most body sites, including the brain, in both immunocompromised and immunocompetent patients. Its elevation to model status for the black fungi is based on its polymorphism, which can be manipulated experimentally to produce for detailed study homogeneous populations each of the morphotypes characteristic in vivo and in vitro of all of the other pathogenic black fungi. In addition, and to date, it is the only black fungal pathogen of humans for which numerous molecular tools are available for study of its biology and the basis of its virulence. Matsumoto, T., L. Ajello, T. Matsuda, P. J. Szaniszlo and T. J. Walsh. Developments in hyalohyphomycosis and phaeohyphomycosis. J. Med. Vet. Mycol. Suppl. 32 (1994) 329-349. Szaniszlo, P. J. Molecular genetic studies of the model dematiaceous pathogen Wangiella dermatitidis. Int. J. Med. Microbiol. 292 (2002) 283-289. Szaniszlo, P. J. Virulence factors in black molds with emphasis on melanin, chitin and Wangiella as a molecularly tractable model, p. 407-428. In: J. Heitman, S. G. Filler, J. E. Edwards and A. P. Mitchell (ed). Molecular Principles of Fungal Pathogenesis. (2006). ASM Press, Washington, D.C.

What is Wangiella (Exophiala) dermatitidis (in more detail)?

Wangiella dermatitidis is a pathogen of humans that causes a disease known as phaeohyphomycosis.^[1] Although typically referred to as a black yeast, this asexual species is, in fact, a conidiogenous mold that has been molecularly classified among the Chaetothyriomycetidae, one of the two subclasses of the Eurotiomycetes class of the Ascomycota.^[2] Traditionally most associated with dermatotropic forms of disease, in the manner of most black fungi, it is being reported with increasing frequency as a systemic pathogen with a marked neurotropic tendency.^[3] Predisposing factors for the systemic forms include cystic fibrosis, lymphocytic leukemia, diabetes mellitus, bronchiectasis, rheumatoid arthritis and catheterization. Initiation of both the dermatotropic and systemic disease forms is attributed to the traumatic implantation of the fungus into tissue, although in some cases the rout of infection is unknown and pulmonary entry has not been ruled out.^[4,5]

In vivo W. dermatitidis is manifested as a plethora of darkly pigmented morphotypes, which include polarized thin-walled and ovoid budding yeast, and septated and branched or unbranched true, moniliform or pseudohyphae and nonpolarized and isotropically enlarged thick-walled forms variously termed sclerotic cells and planate cells, together with an infrequent sclerotic (muriform) body.^[6] The pigmentation of all the morphotypes is due to the deposition into the cell walls of W. dermatitidis of the polymerization product 1,8-dihydroxynaphthalene,^[7] a known virulence factor in this species^[8] and most likely all other of the fungal pathogens of humans similarly melanized. These characteristics, plus the ability of investigators to experimentally manipulate switching among the many morphotypes and to produce them in vitro for study in homogeneous populations,^[9] as well as the increasing molecular tractability of W. dermatitidis, suggested that it would be an exceptional candidate for whole genome sequencing. The data generated are expected to confirm further that this species warrants its status as a model for the black pathogenic fungi. Since the alternate morphotypes of this species are also induced by or have tolerance for a variety of very stressful conditions, such as extremely low pH, nitrogen and calcium limitation, elevated temperatures, and radiation resistance,^[10] it would not be surprising to find that these data also will be useful to those who are studying the variety of nonpathogenic black fungi that exist in nature under these and other extremely stressful conditions.

References

1. Matsumoto, T., L. Ajello, T. Matsuda, P. J. Szaniszlo and T. J. Walsh. Developments in hyalohyphomycosis and phaeohyphomycosis. J. Med. Vet. Mycol. Suppl. 32 (1994) 329-349.
2. Geiser, D. M., C. Gueidan, J. Miadlikowska, F. Lutzoni, F. Kauff, V. Hofstetter, E. Fraker, C. L. Schoch, L. Tibell, W. A. Untereiner, and A. Aptroot. 2006. Eurotiomycetes: Eurotiomycetidae and Chaetothyriomycetidae. Mycologia 98, 1053-1064.
3. Matsumoto, T., Matsuda, T., McGinnis, M.R., Ajello. L., 1993. Clinical and mycological spectra of Wangiella dermatitidis infections. Mycoses 36,145-155.
4. Lebecque, P., A. Leonard, H. Daniel, R. Gregory, A. Boreras, T. Leal and F. Symoens. 2010. Exophiala (Wangiella) dermatitidis and cystic fibrosis - prevalence and risk factors. Med. Mycol. Suppl. 4854-59.
5. Horre, R., and G.S. de Hoog. 1999. Primary cerebral infections by melanized fungi: a review. p.176-193. In G. S. de Hoog (ed.). Studies in Mycology 43. Centraalbureau voor Schimmelcultures, Baarn/Delft, The Netherlands.
6. Szaniszlo, P. J. Molecular genetic studies of the model dematiaceous pathogen Wangiella dermatitidis. Int. J. Med. Microbiol. 292 (2002) 283-289.
7. Wheeler, M. H., D. Abramczyk, L. S. Puckhaber, M. Naruse, Y. Ebizuka, I. Fujii and P. J. Szaniszlo. A new biosynthetic step in the melanin pathway of Wangiella (Exophiala) dermatitidis: evidence for 2-acetyl-1,3,6,8-tetrahydroxynaphthalene as a novel precursor. Eukaryot. Cell 7 (2008) 1699-1711.
8. Feng, B., X. Wang, M. Hauser, S. Kauffmann, S. Jentsch, G. Haase, J. M. Becker, and P. J. Szaniszlo. Molecular cloning and characterization of WdPKS1, a gene involved in melanin biosynthesis and virulence in Wangiella (Exophiala) dermatitidis. Infect. Immun. 69 (2001) 1781-1794.
9. Abramczyk, D., C. Park, and P. J. Szaniszlo. Cytolocalization of the class V chitin synthase in the yeast, hyphal and sclerotic morphotypes of Wangiella (Exophiala) dermatitidis. Fungal Gen. Biol. 46 (2009) 28-41.
10. Szaniszlo, P. J. Virulence factors in black molds with emphasis on melanin, chitin and Wangiella as a molecularly tractable model, p. 407-428. In: J. Heitman, S. G. Filler, J. E. Edwards and A. P. Mitchell (ed). Molecular Principles of Fungal Pathogenesis. (2006). ASM Press, Washington, D.C.

     Phaeohyphomycosis, in the broad sense, sometimes is said to include several additional human syndromes,  which include black-grained mycetoma, chromoblastomycosis, tinea nigra, black piedra, keratitis, and onychomycosis.