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School of Molecular & Biomedical Science
The University of Adelaide
AUSTRALIA 5005

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Dr David Ellis
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Exserohilum sp.

Colonies are grey to blackish-brown, suede-like to floccose in texture, and have an olivaceous black reverse. Conidia are straight, curved or slightly bent, ellipsoidal to fusiform and are formed apically through a pore (poroconidia) on a sympodially elongating geniculate conidiophore. Conidia have a strongly protruding, truncate hilum and the septum above the hilum is usually thickened and dark. The end cells are often paler than the other cells and the walls are often finely roughened. Conidial germination is bipolar.

Exserohilum rostratum Exserohilum rostratum
Conidiophores and conidia of Exserohilum rostratum.

The genus Exserohilum may be differentiated from the closely related genera Bipolaris and Drechslera by forming conidia with a strongly protruding truncate hilum (i.e. exserted hilum). The hilum is defined as "a scar on a conidium at the point of attachment to the conidiophore". In Drechslera species, the hilum does not protrude whereas in Bipolaris species the hilum protrudes only slightly.

 

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

Antifungal
MIC ug/mL
Antifungal
MIC ug/mL
Antifungal
MIC ug/mL
Range
Range
Range
Amphotericin B
0.125-2
Itraconazole
0.03-0.5
Voriconazole
0.03-0.5

 

Clinical significance:

Exserohilum species are common environmental moulds found in soil and on plants, especially grasses. Several species have been reported as agents of phaeohyphomycosis, notably E. rostratum (= E. halodes), E. meginnisii and E. longirostratum.  Clinical manifestations include mycotic keratitis, subcutaneous phaeohyphomycosis, endocarditis, osteomyelitis and sinusitis in both normal and immunosuppressed patients.

Mycosis: Phaeohyphomycosis

Further reading:

Domsch, K.H., W. Gams, and T.H. Anderson. 1980. Compendium of soil fungi. Volume 1. Academic Press, London, UK.

McGinnis, M.R., M.G. Rinaldi and R.E. Winn. 1986. Emerging agents of Phaeohyphomycosis: pathogenic species of Bipolaris and Exserohilum. J. Clin. Microbiol. 24:250-259.