Aspergillus species
A.
flavus
Link
- click
here
for clinical material. More images
Colony characteristics. Colonies (CzA) yellowish-green,
consisting of a dense felt of conidiophores.
Colonies on Czapek agar at 25°C attaining a diameter of 3-5 cm within 7 days, usually consisting of a dense felt of yellow-green conidio-phores. Conidial heads typically radiate, later splitting into several loose columns, yellow-green becoming dark yellow-green. Conidiophores hya-line, coarsely roughened, up to 1.0 mm (some isolates up to 2.5 mm) in length. Vesicles globose to subglobose, 25-45 µm in diam. Phialides borne directly on the vesicle or on the metulae, 6-10 x 4.0-5.5 µm. Metulae 6.5-10 x 3-5 µm. Conidia globose to subglobose, 3.6 µm in diam, pale green, echinulate. Sclerotia often produced in fresh isolates, variable in shape and dimension, often brown to black.
Colonies on MEA growing faster, otherwise similar. Poor growth on CREA, orange reverse on AFPA.
Microscopy. Conidiophore stipes rough walled, hyaline. Conidial heads radiate, uni- and biseriate. Vesicles spherical, 25-45 micrometre diam. Conidia echinulate, (sub)spherical, 3.5 micrometre diam. Sclerotia may be present.
Differential diagnosis. The species is easily distinguished from A. fumigatus by the following characters; yellow-green colonies; mature vesicles bearing phialides over their entire surface.
Pathogenicity.
The species is one of the main agents of human allergic bronchial
aspergillosis. The species also occurs in external ears and may be involved
in otitis (Jesenka et al., 1992). Systemic infections occur in leukemic
patients (Shitara et al., 1993). It is also one of the common agents of
mycotic sinusitis (Drakos et al., 1993; El-Shoura, 1993). Cutaneous aspergillosis
is rare (Harmon et al., 1993). Also cases of aspergillosis in other vertebrates
have been reported (Barton et al., 1992). The species is particularly
found in the Americas.
Habitat: Food. Common in (ground)nuts, spices, oil seeds, cereals, occasionally in dried fruits (e.g. figs).
References
- 
Selected historical references are listed below
Barton, J.T., Daft, B.M., Read, D.H., Kinde, H. & Bickford, A.A., (1992). Tracheal aspergillosis in 61 2 week-old chickens caused by Aspergillus flavus. Avian Dis. 36: 1081-1085.
Drakos, P.E., Nagler, A., Or, R., Naparstek, E., Kapelushnik, J., Engelhard, D., Rahav, G., Ne'emean, D. & Slavin, S., (1993).Invasive fungal sinusitis in patients undergoing bone marrow transplantation. Bone Marrow Transpl. 12: 203-208.
El-Shoura, S., (1993). Ultrastructural interaction between multinucleate giant cells and the fungus in aspergillomas of human paranasal sinuses. Virchovs Arch. B-64: 395-400.
Harmon, C.B., Daniel, W.P. & Peters, M.S., (1993). Cutaneous aspergillosis complicating pyoderma gangrenosum. J. Am. Acad. Dermatol. 29: 656-658.
Jesenka, Z., Durkovsky, J., Rosinsky, I., Polak, M., Zamboova, E. & Baca, B., (1992). Filamentous micromycetes in otitis. Cesk Epidemiol. Mikrobol. Imunol. 41: 337-341
Samson, R.A., Hoekstra, E.S. & Frisvad, J.C. 2004, Introduction to food- and airborne fungi: 72
Shitara, T., Yugami, S.-I., Sotomatu, M., Oshima, Y., Ijima, H., Kuroume, T. & Matsumoto, T., (1993). Invasive aspergillosis in leukemic children. Pediatr. Hematol. Oncol. 10: 169-174.