Introduction
Table of Contents
- Aspergillus niger
- A saprophytic mold widely found in soil, decaying vegetation, and indoor environments.
- Known for black conidial heads, rapid growth, and production of industrially important enzymes and organic acids.
- Clinically, it may cause otitis externa, aspergilloma, and rarely invasive disease in immunocompromised hosts.
- Aspergillus fumigatus
- Thermotolerant mold is the most common cause of invasive aspergillosis in humans.
- Found in soil, compost, and decaying organic matter.
- Characterized by green-blue colonies and compact conidial heads.
- Causes allergic bronchopulmonary aspergillosis (ABPA), chronic pulmonary aspergillosis, and invasive aspergillosis in immunocompromised patients.
Key Differences: Aspergillus niger vs Aspergillus fumigatus
| Feature | Aspergillus niger | Aspergillus fumigatus |
|---|---|---|
| Colony color (SDA) | Black, powdery colonies | Blue-green to gray-green colonies |
| Growth rate | Rapid, abundant sporulation | Moderate, compact colonies |
| Conidial heads | Large, radiate, globose | Columnar, compact |
| Conidia | Rough, black, spherical | Smooth to rough, greenish |
| Optimal growth temperature | 25–30 °C | 37–45 °C (thermotolerant) |
| Clinical relevance | Otomycosis, aspergilloma, rare invasive disease | Otomycosis, aspergilloma, and rare invasive disease |
| Virulence | Lower virulence, opportunistic | High virulence, leading fungal killer in immunocompromised |
| Industrial use | Citric acid, enzymes (amylase, protease) | Limited industrial use |
| Histopathology | Septate hyphae, dichotomous branching, black pigment | Septate hyphae, dichotomous branching (classic invasive mold) |
Keynotes
- A. fumigatus is the most pathogenic Aspergillus species, while A. niger is more often an environmental contaminant or cause of localized infections.
- Both show septate, dichotomously branching hyphae microscopically, making culture essential for differentiation.
- Temperature preference distinguishes them: A. fumigatus thrives at human body temperature, explaining its clinical dominance.
- A. niger is important in industrial biotechnology, whereas A. fumigatus is primarily significant in clinical mycology.
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