DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 3
A ubiquitous genus containing common saprophytes in soil and air, and plant pathogens.
A. infectoria is the most common clinical species (Pastor and Guarro, 2008). Although
usually seen as saprophytic contaminants, Alternaria species in particular A. alternata
and A. infectoria are recognised causative agents of subcutaneous phaeohyphomycosis
and mycotic keratitis. They are a rare cause of onychomycosis, usually following trauma
to the nail.
RG-1 organisms.
Alternaria Nees ex Fries
Morphological Description: Colonies are fast growing, black to olivaceous-black or
greyish, and are suede-like to floccose. Microscopically, branched acropetal chains
(blastocatenate) of multicellular conidia (dictyoconidia) are produced sympodially from
simple, sometimes branched, short or elongate conidiophores. Conidia are obclavate,
obpyriform, sometimes ovoid or ellipsoidal, often with a short conical or cylindrical beak,
pale brown, smooth-walled or verrucose. Temperature: optimum 25-28 O C; maximum
31-32 O C.
Molecular Identification: Multilocus genotype studies have shown the Alternaria
complex currently comprises nine genera and eight Alternaria sections (Woudenbert et
al. 2013). ITS sequencing is sufficient for genus and usually species level identification
and can clearly differentiate A. alternata and A. infectoria (Pastor and Guarro, 2008).
However, it is estimated that >14% of GenBank sequences of Alternaria species
are misclassified, so unknown sequences should be compared to those of wellcharacterised
reference strains (Woudenberg et al. 2013).
Comments: Alternaria species soon lose their ability to sporulate in culture. Potato
dextrose agar and cornmeal agar are the most suitable media to use, and incubation
under ultra-violet light is recommended to maintain sporulation.
Key Features: Dematiaceous hyphomycete producing chains of darkly pigmented,
ovoid to obclavate dictyoconidia, often with short conical or cylindrical beaks.
References: Simmons (1967, 2007), Ellis (1971), Domsch et al. (2007), Samson et al.
(1995), de Hoog et al. (2000, 2015), Pryor and Gilbertson (2000), de Hoog and Horre
(2002), Pastor and Guarro (2008), Woudenberg et al. (2013).
Antifungal Susceptibility: Alternaria spp. (Australian National data); MIC µg/mL.
No 8
AmB 10 3 1 4 2
VORI 10 1 3 5 1
POSA 9 2 1 5 1
ITRA 10 1 1 2 5 1