Aspergillus flavus
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Aspergillus flavus
Aspergillus flavus is a fungus and a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce significant quantities of aflatoxin, a carcinogenic and acutely toxic compound. A. flavus spores are allergenic. A. flavus sometimes causes losses in silkworm hatcheries.
| Kingdom | Fungi |
|---|---|
| Phylum | Ascomycota |
| Class | Eurotiomycetes |
| Order | Eurotiales |
| Family | Trichocomaceae |
| Genus | Aspergillus |
| Species | A. flavus |
| Binomial | Actinobacillus pleuropneumoniae |
Contents |
Surface Characteristics
The cell surface consists of various polysaccharides such as galactomannans.Galactomannans are composed of an α-1,6-linked mannan backbone substituted with mannopyranose oligosaccharides and immunodominant terminal galactofuranose present either singly or linked to oligogalactosides. The wide distribution and similar chemical structure of the galactomannans have been responsible for serologic cross-reactions between different serotypes.
Transmission
The fungus overwinters either as mycelium or as resistant structures known as sclerotia. The sclerotia either germinate to produce additional hyphae or they produce conidia (asexual spores), which can be dispersed in the soil and air. These spores are carried to the maize ears by insects or wind where they germinate and infect maize kernels.
Pathogenic Activity
Aspergillus flavus can also be pathogenic on several plant and animal species, including humans and domestic animals. The fungus can infect seeds of corn, peanuts, cotton, and nut trees. The fungus can often be seen sporulating on injured seeds such a maize kernels as shown above. Often, only a few kernels will be visibly infected
Virulence
Aspergillus flavus is also the second leading cause of aspergillosis in humans. Patients infected with A. flavus often have reduced or compromised immune systems. Unlike most fungi, Aspergillus flavus is favored by hot dry conditions. The optimum temperature for growth is 37 C (98.6 F), but the fungus readily grows between the temperatures of 25-42 C (77-108 F), and will grow at temperatures from 12-48C (54-118 F). Such a high temperature optimum contributes to its pathogenicity on humans. Particularly common clinical syndromes associated with A. flavus include chronic granulomatous sinusitis, keratitis, cutaneous aspergillosis, wound infections and osteomyelitis following trauma and inoculation
References
M. T. Hedayati, A. C. Pasqualotto, P. A. Warn, P. Bowyer and D. W. Denning. [2007] Aspergillus flavus: human pathogen, allergen and mycotoxin producer. Microbiology 153: 1677-1692 Ref
