Hortaea werneckii

Synonyms: Cladosporium werneckii; Exophiala werneckii; Phaeoannellomyces werneckii

Colonies are slow growing, initially mucoid, yeast-like and shiny black. With age they develop abundant aerial mycelia and become dark olivaceous in color.  Microscopically, colonies consist of brown to dark olivaceous septate hyphal elements and numerous 2-celled, pale brown, cylindrical to spindle-shaped yeast-like cells that taper towards the ends to form an annellide.  Most yeast-like cells also have prominent darkly pigmented septa.  Annellides may also arise from the hyphae. Conidia are l to 2-celled, cylindrical to spindle-shaped, hyaline to pale brown and usually occur in aggregated masses.  RG-1 organism.

Conidia of Hortaea werneckii.

MIC data is limited.  Antifungal susceptibility testing of individual strains is recommended.

Clinical significance:

Hortaea werneckii is a common saprophytic fungus believed to occur in soil, compost, humus and on wood in humid tropical and sub-tropical regions and is the causative agent of tinea nigra in humans. Tinea nigra is a superficial fungal infection of skin characterized by brown to black macules which usually occur on the palmar aspects of hands and occasionally the plantar and other surfaces of the skin. Lesions are non-inflammatory and non-scaling. Familial spread of infection has been reported.

Mycosis: Tinea nigra

Further reading:

Rippon, J.W. 1988. Medical Mycology. 3rd Edition. W.B. Saunders Co., Philadelphia, USA.