Aspergillus  Mold

Photo of Dr. Sharol with a big smile in oval photo frame
Aspergillus flavus in petri dish.
USDA photo - ARS and Peggy Greb

Aspergillus Genus

The Aspergillus genus are found worldwide in the soil, forage products for animals, food products, in organic debris, in composting material, and in dust. They are considered to be weak plant pathogens. However two of the species, Aspergillus flavus and A. parasiticus are known to produce potent toxins called afflatoxins on certain food crops. Some Aspergillus species also make the potent kidney toxin, ochratoxin. These include the more notable  A. ochraceus,  A. carbonarius and A. niger.  Only a small amount of strains of A. niger make ochratoxin.  In the photo on left is Aspergillus flavus.

Aspergillus is found on many foods. It is almost always on pepper. In one study 100%of pepper samples, and black tea samples had A. species and 12-66% of fruits, 27% of herbal teas and 20% of freeze dried soup samples contained Aspergillus spp.

Strains of Aspergillus niger (photos on right) that do not produce ochratoxin are used to process some food products. Aspergillus niger is used widely in the production of enzymes, such as alpha-amylase, cellulases, lactase, invertase, and pectinase. Aspergillus niger is also used to make fructooligosaccharides and citric acid. It is important to ensure that industrial strains are nonproducers of ochratoxin.

When testing Aspergillus niger strains for production of ochratoxin A, it was found that 3-10% of them were able to produce ochratoxin A.  Luckily, most strains of A. niger do not make ochratoxin A, as A. niger is found in the soil everywhere.

 

The Two Toxic Mycotoxins Associated With Aspergillus Species

Various Aspergillus species produce the two toxic mycotoxins called aflatoxin and ochratoxin.

Aspergillus niger growing on plate.
Aspergillus niger growing on onion.

Aflatoxin

Aspergillus produces the mycotoxin called Aflatoxin. It was discovered after 10,000 turkeys died from contaminated peanuts in England. Aflatoxin has been the cause of deaths in humans and animals as well as birds. They are known to be liver toxins, teratogenic (causes malformations of an embryo or fetus) and mutagenic (causes mutations in genetic material).

The food/forage crops that are known to be especially susceptible to Aspergillus flavus and parasiticus are peanuts, corn and cottonseed. A. flavus is more common on corn and cottonseed, while A. parasiticus is more common on peanuts. Those corns containing higher oil contents are at greater risk for aflotaxins than normal hybrids during the growing process.

Aflatoxins contaminate many crops including corn, peanuts, cottonseed, brazil nuts, pistachios dried coconut, dried figs, and spices. They are common in hot and humid regions of the world. Aflatoxin contamination is worse during drought years.

I have written up extensive data on aflatoxins and you can find it here. I am currently working on data for the oher mycotoxins listed below.

Ochratoxin

Aspergillus produces the mycotoxin called ochratoxin (OTA). OTA is a potent kidiney mycotoxin, and also displays other adverse effects such as liver toxicity,  immunosuppression, and is a teratogen and carcinogen.

Ochratoxins occur in nature as Ochratoxin A (OTA), B (OTB), and C (OTC). Ochratoxin A is the most prevalent toxin and the most toxic followed by OTB and OTC. Ochratoxin A, B and C are produced by Penicillium species also.

Exposure to ochratoxins is largely through food contamination and the most common food to be contaminated is grains. Skin contact and inhalation are known to also cause toxicity. Inhalation is usually from dust in commercial areas where grains are being stored and/or processed. Ochratoxin may also be found in water-damaged buildings. One clinical study identified OTA in 83% of over 100 individuals tested with chronic illness and a history of water-damaged building exposure.

Concerns regarding exposure to ochratoxin have primarily centered on exposure to food contaminated with OTA such as wine, beer, coffee, dried vine fruit, grape juices, pork, poultry, dairy, spices, and chocolate. Toxicity from ochratoxin is considered serious enough that it is among approximately 20 mycotoxins monitored in food.

Read more about Ochratoxin here.

Aspergillosis

This is a group of disease processes that are caused as a result of Aspergillus infections. This is an infection where the fungus grows in the person, and it is not a reaction to mycotoxins made by the fungus as we discuss in most other articles about mold and mycotoxins. Sometimes molds can actually grow inside a person, usually in the respiratory tract. This is a fungus that is known for taking root inside of people. The people that are more susceptible to aspergillus spp. taking a liking to them are those that are immunocompromised and those that work in situations where Aspergillus spores are airborne such as agricultural, or horticultural workers inhaling dust from spores. It is also a cause of fungal ear infections in tropical areas.

The Categories Of Disease Caused By Aspergillus

  • Invasive Aspergillosis
  • Allergic Bronchopulmonary Aspergillosis
  • Chronic Pulmonary Aspergillosis
  • Aspergilloma

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