Exophiala jeanselmei
Synonym: Phialophora jeanselmei
E. jeanselmei has long been recognised as heterogeneous (de Hoog 1977). Recent molecular studies have redefined Exophiala jeanselmei and three additional species have been identified: E. oligosperma, E. nishimurae, and E. xenobiotica (Vitale and de Hoog, 2002 , de Hoog et al. 2003, 2006). These species are morphologically very similar and can best be distinguished by genetic analysis.
Conidiogenous cells are predominantly annellidic and erect, multicellular conidiophores are absent. No growth at 40C.
| E. jeanselmei | Mature conidiogenous cells rocket-shaped, slightly darker than the supporting hyphae, with regular tapering annellated zones. |
E. oligosperma |
Mature conidiogenous cells remain concolorous with supporting hyphae and may be intercalary and lateral, the latter being flask or rocket-shaped. Annellated zones have the appearance of inconspicuous flat scars. Chlamydospores are absent. |
| E. nishimurae | Similar morphology to E. oligosperma, however large chlamydospore-like cells are present. |
| E. xenobiotica | A segregant genotype of the E. jeanselmei complex with less melanised conidiogenous cells. |
Colonies are initially smooth, greenish-grey to black, mucoid and yeast-like, becoming raised and developing tufts of aerial mycelium with age, often becoming dome-shaped and suede-like in texture. Reverse is olivaceous-black. Numerous ellipsoidal, yeast-like, budding cells are usually present, especially in young cultures. Scattered amongst these yeast-like cells are larger, inflated, subglobose to broadly ellipsoidal cells (germinating cells) which give rise to short torulose hyphae that gradually change into unswollen hyphae. Conidia are formed on lateral pegs either arising apically or laterally at right or acute angles from essentially undifferentiated hyphae or from strongly inflated detached conidia. Conidiogenous pegs are 1-3 µm long, slightly tapering and imperceptibly annellate. Conidia are hyaline, smooth, thin-walled, broadly ellipsoidal, 3.2-4.4 x 1.2-2.2 µm, and with inconspicuous basal scars. Cultures grow at 37C but not at 40C. RG-2 organism.
E. jeanselmei has a world-wide distribution and is a recognised causative agent of mycetoma and phaeohyphomycosis in humans.
Culture of Exophiala jeanselmei.
Yeast-like cells, torulose hyphae, conidiophores,
annellides and conidia of E. jeanselmei.
Annellides, conidia and conidiogenous pegs (annellides) on yeast-like cells
and torulose hyphae of E. jeanselmei.
MIC data is limited. Antifungal susceptibility testing of individual strains is recommended.
| Antifungal | MIC ug/mL | Antifungal | MIC ug/mL |
||
Range |
MIC90 |
Range |
MIC90 |
||
| Itraconazole | 0.03-2 |
0.5 |
Amphotericin B | 0.03-4 |
0.5 |
| Voriconazole | 0.06-2 |
0.5 |
Posaconazole | 0.25-0.5 |
0.5 |
Clinical significance:
Exophiala species are common environmental fungi often associated with decaying wood and soil enriched with organic wastes. However, several species notably E. jeanselmei, E. moniliae and E. spinifera, are well documented human pathogens. Clinical manifestations include mycetoma (especially for E. jeanselmei), localized cutaneous infections, subcutaneous cysts, endocarditis and cerebral and disseminated infections. Phaeohyphomycosis caused by Exophiala species has been reported in both normal and immunosuppressed patients.
Mycosis: Phaeohyphomycosis
Further reading:
De Hoog, G.S., and E.J. Hermanides-Nijhof. 1977. The black yeasts and allied hyphomycetes. Studies in Mycology No. 15. Centraalbureau voor Schimmelcultures, Baarn, The Netherlands.
Kwon-Chung, K.J. and J.E. Bennett. 1992. Medical Mycology. Lea & Febiger, Philadelphia and London
