Date: 26 November 2013
Aspergillus flavus
Copyright:
© Fungal Research Trust
Notes:
Colonies on CYA 60-70 mm diam, plane, sparse to moderately dense, velutinous in marginal areas at least, often floccose centrally, sometimes deeply so; mycelium only conspicuous in floccose areas, white; conidial heads usually borne uniformly over the whole colony, but sparse or absent in areas of floccose growth or sclerotial production, characteristically Greyish Green to Olive Yellow (1-2B-E5-7), but sometimes pure Yellow (2-3A7-8), becoming greenish in age; sclerotia produced by about 50% of isolates, at first white, becoming deep reddish brown, density varying from inconspicuous to dominating colony appearance and almost entirely suppressing conidial production; exudate sometimes produced, clear, or reddish brown near sclerotia; reverse uncoloured or brown to reddish brown beneath sclerotia. Colonies on MEA 50-70 mm diam, similar to those on CYA although usually less dense. Colonies on G25N 25-40 mm diam, similar to those on CYA or more deeply floccose and with little conidial production, reverse pale to orange or salmon. No growth at 5°C. At 37°C, colonies usually 55-65 mm diam, similar to those on CYA at 25°C, but more velutinous, with olive conidia, and sometimes with more abundant sclerotia.
Sclerotia produced by some isolates, at first white, rapidly becoming hard and reddish brown to black, spherical, usually 400- 800 µm diam. Teleomorph not known. Conidiophores borne from subsurface or surface hyphae, stipes 400 µm to 1 mm or more long, colourless or pale brown, rough walled; vesicles spherical, 20-45 µm diam, fertile over three quarters of the surface, typically bearing both metulae and phialides, but in some isolates a proportion or even a majority of heads with phialides alone; metulae and phialides of similar size, 7-10 µm long; conidia spherical to subspheroidal, usually 3.5-5.0 µm diam, with relatively thin walls, finely roughened or, rarely, smooth.
Distinctive features
Aspergillus flavus is distinguished by rapid growth at both 25°C and 37°C, and a bright yellow green (or less commonly yellow) conidial colour. A. flavus produces conidia which are rather variable in shape and size, have relatively thin walls, and range from smooth to moderately rough, the majority being finely rough.
Images library
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Image A. Scan shows large bore needle in one of the cavities on the right. The contrast media is mixed with amphotericin B and is whiter than surrounding lung tissue and fungal ball. The contrast surrounds the aspergilloma present in this cavity. Some of the contrast has fallen by gravity in another cavity anteriorly below the one being injected, showing communication between the cavities.
Image B. Scan showing contrast media mixed with amphotericin B injected into a multicystic cavity in the right upper lobe. The contrast (white) flows around the aspergilloma present in this cavity. The contrast falls by gravity posteriorly.
Image C. The opposite lung shows multiple empty cystic spaces with little normal lung.
Image D. There is substantial pleural thickening surrounding the irregular cavity containing the aspergilloma.
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Extensive multilobar, varicose bronchiectasis, with some cyst formation most marked on the left anteriorly. Also some inhomogeneity of the pulmonary parenchyma secondary to air trapping in several affected segments.
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CT scans of thorax. Anterior left-sided bronchiectasis with extensive mucous plugging and with some proximal bronchiectasis and plugging on the right.
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Bilateral multilobar varicose bronchiectasis affecting the segmental and small order bronchi, with some distal plugging.
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T1 weighted, gadolinium enhanced magnetic resonance brain scan. This 43 year-old alcoholic woman underwent laparoscopic cholecystectomy in January 2001. Ten days after surgery, she became confused, dysphasic and eventually had tonic-clonic seizures. A CT scan showed non-communicating hydrocephalus with ventriculitis. She underwent many complicated neurosurgical interventions, and received long term broad-spectrum antimicrobials and dexamethasone. One month later, she had generalized seizures, and a large abscess was observed on scan (see images). A heavy growth of A. fumigatus was retrieved from the abscess, and amphotericin B and 5-flucytosine were started. Antifungal therapy was changed voriconazole due to intolerance to amphotericin B and worsening disorientation. Voriconazole dosing (which varied from 300mg to 100mg twice daily) was guided by plasma concentrations as enzyme induction with rifampicin and carbamazepine, and reduction in clearance with alcoholic liver disease complicated her voriconazole dosing. Steroids were gradually reduced. She had a good recovery and completed 9 months of voriconazole.
Despite air filtration in the operating rooms, she apparently acquired an intra-operative infection, probably accelerated in presentation by concurrent dexamethasone. Rapid diagnosis and optimization of voriconazole dosing lead to a good outcome.
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Allergic Broncho-pulmonary aspergillosis. Pt CT. Extensive severe saccular bronchiectasis of the left lower lobe and to a lesser extent of the left upper and right lower lobe.
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Ct scan of chest. This patient with severe ABPA, serologically and radiologically, developed a spectrum of lesions in the lung. In this cut, a cavitating infiltrate in the anterior segment of the left upper lobe was visualised together with some bronchial thickening and bronchiectasis in the left upper and lower lobe.
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