Category:Dematiaceous molds
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- Phenotypic grouping of fungi based on the presence of melanin
Background
- Melanin is a virulence factor which protects again proteolytic enzymes, oxydation, and phagocytosis
- Includes so-called "black yeast", which appear yeast-like early in culture
- Colonies may grow slowly or quickly (e.g. within a week)
- Pigment may take time to develop, but most will become olive, brown, or black
Microscopy
- Genus identification is made based on a number of microscopic features
- Annelides are rings that appear following release of conidia at the apex
- Phialides are cylindrical or flask-shaped cells from which conidia are formed
- Geniculate pattern is a zig-zag caused by bending at the point of connection for each conidiophore
- Blastoconidia
- Arthroconidia
- Chlamydoconidia
- Large conidia
- Single large muriform conifia suggests Epicoccum, Alternaria, and Ulocladium
- Single large conidia with transverse septum, suggests Curvularia or Exserohilum
- Small conidia
- Geniculate conidiophores suggests Fonsecaea
- Conidia in chains suggests Cladosporium or Cladophialophora
- Conidia on denticles (stems) suggests Madurella or Neoscytalidium
- Conidia by phialides suggests Phaeoacremonium
- Unique reproductive bodies
- Perithecia covered with hairs suggests Chaetomium
- Pycnidia with ostioles (holes) suggests Phoma
- Special tests, including thermal tolerance and germ tube test, can help to distinguish species within a genus
- However, species identification is difficult without molecular assays
Clinical Manifestationss
- Phaeohyphomycosis typically refers to cutaneous, subcutaneous, and disseminated disease, and is often acquired by traumatic innoculation
- Superficial cutaneous infection
- Subcutaneous phaeohyphomycosis
- Disseminated disease, more common in immunocompromised patients
- Chromoblastomycosis
- Mycetoma
| Disease | Organisms | Notes |
|---|---|---|
| Localized cutaneous infection or abscess | Alternaria, Exophiala, Phialophora | Traumatic inoculation. Can become disseminated if immunocompromised. |
| Mycetoma | Madurella, Exophiala jeanselmei, Leptosphaeria | Spectrum from cutaneous to deep bone. Chronic draining, including granules. |
| Chromoblastomycosis | Cladophialophora carrionii, Fonsecaea, Phialophora | Chronic subcutaneous infection with sclerotic or muriform bodies |
| Keratitis | Most common in India. Usually from traumatic inoculation | |
| Black piedra | Piedraia hortae | Present in the tropics. Involves only the hair. |
| Allergic sinusitis | Bipolaris, Curvularia, Exserohilum | More common in an atopic or asthmatic patient. |
| Allergic bronchopulmonary disease | Bipolaris, Curvularia | Rare. |
| Pulmonary disease | Scedosporium prolificans, Cladophialophora bantiana | Mostly in immunocompromised patients. |
| Cerebral disease | Cladophialophora bantiana, Verruonis gallopava, Exserohilum rostratum, Rhinocladiella, Exophiala dermatitidis | Occurs in immunocompetent people. Species involved varies geographically. |
| Disseminated disease | Curvularia, Exophiala, Bipolaris, Alternaria, Verruconis | Mostly in immunocompromised patients. |
Further Reading
- ESCMID and ECMM joint clinical guidelines for the diagnosis and management of systemic phaeohyphomycosis: diseases caused by black fungi. Clin Micro Infection. 2014 20(Suppl. 3):47-75. doi: 10.1111/1469-0691.12515
Pages in category "Dematiaceous molds"
The following 9 pages are in this category, out of 9 total.
