Aspergillus niger

The Fungus:

• Aspergillus niger is one of Aspergillus’ four species known to cause invasive disease in humans (others being A fumigatus, A flavus and A terreus).
• However, it is possibly the least common among the four. FDA classed it safe [GRAS] for industrial use.
• In nature, it is found on soils, plants, food and spices.

Identification:

It initially forms white colonies with a yellow back, which quickly becomes black. Conidia is rough, brownish-black, biseriate, and covers the entire vesicle.

A key feature in diagnosing A. niger infection is the presence of calcium oxalate crystals on pathological examination. The presence of crystals can be taken as an indication of A niger infection.

Virulence factor:

Toxin – malformin C, ochratoxin A

Infection:

• It is the commonest cause of otomycosis – colonising the ear canal, appearing as a black tuft.
• Cutaneous infection [Loudon, 1996].
• Pulmonary infection and invasive aspergillosis.

Treatment:

Otomycosis –

• Cleaning and topical antifungals (clotrimazole, miconazole).
• Severe infection may need oral antifungals.
• Invasive diseases may need IV antifungal.

Invasive aspergillosis –

• Voriconazole or isavuconazole +/- Echinocandin
• Amphotericin B preparations.

Non-medical use –

Aspergillus niger has much non-medical use – production of citric acid, waste management, and biotransformation.