DESCRIPTIONS OF MEDICAL FUNGI

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Descriptions of Medical Fungi
Apophysomyces complex
Historically the genus Apophysomyces was considered to be monotypic and A. elegans
was reported to be an important human pathogen in immunocompetent patients
following traumatic implantation. A phylogenetic revision of the genus has identified
three additional species, A. ossiformis, A. trapeziformis and A. variabilis. Many isolates
previously identified as A. elegans, now appear to be A. variabilis (Alvarez et al. 2010a).
Molecular identification is required to accurately differentiate these species.
Morphological characteristics overlap so identification and reporting of Apophysomyces
complex is recommended for most diagnostic laboratories.
Molecular Identification: The ITS region and D1/D2 domain may provide for accurate
species identification (Halliday et al. 2015). ITS restriction fragment length polymorphism
analysis has also been described (Chakrabarti et al. 2003).
RG-2 organism.
Apophysomyces elegans Misra, Srivastava & Lata
Morphological Description: Colonies are fast growing, white, becoming brownish
grey with age, downy with no reverse pigment, and are composed of broad, sparsely
septate (coenocytic) hyphae. Sporangiophores are unbranched, straight or curved,
slightly tapering towards the apex, up to 540 µm long, 3-6 µm in width near the
apophysis, and hyaline when young but developing a light to dark brown pigmentation
and a conspicuous subapical thickening 10-16 µm below the apophysis with age.
Sporangiophores arise at right angles from the aerial hyphae and often have a septate
basal segment resembling the “foot cell” commonly seen in Aspergillus. Rhizoids are
thin-walled, subhyaline and predominantly unbranched. Sporangia are multispored,
small (20-58 µm diameter), typically pyriform in shape, hyaline at first, sepia-coloured
when mature, with distinct apophyses and columellae. Columellae are hemispherical
in shape and the apophyses are distinctly funnel or bell-shaped. Sporangiospores are
smooth-walled, subspherical to cylindrical, (5-8 x 4-6 µm), subhyaline to sepia in mass.
Good growth at 26 O C, 37 O C and 42 O C.
RG-2 organism.
Apophysomyces variabilis Alvarez et al.
Morphological Description: Colonies are fast growing, whitish with scarce aerial
mycelium and no reverse pigment. Sporangiophores are erect, generally arising singly,
unbranched, slightly tapering towards the apex, up to 100-400 µm long, 2-3.5 µm in
width near the apophysis, hyaline when young but developing a light greyish brown
pigmentation with age. Sporangia are multispored, small (15-50 µm diameter), typically
pyriform in shape, hyaline at first, sepia-coloured when mature, with distinct apophyses
and columellae. Columellae are hemispherical in shape and the apophyses are short
and distinctly funnel-shaped. Sporangiospores are smooth-walled, variable in shape,
trapezoid, ellipsoidal, sub-triangular or claviform, (5-14 x 3-6 µm), subhyaline to sepia
in mass. Good growth at 26 O C, 37 O C and 42 O C.