Fruiting Body of Aspergillus

What is it, Treatment, and More

Author: Lily Guo

Editors: Alyssa Haag, Ian Mannarino, MD, MBA

Illustrator: Jillian Dunbar

Copyeditor: Joy Mapes

What is a fruiting body of Aspergillus?

A fruiting body of Aspergillus refers to the cluster of spores produced by the fungus Aspergillus. It is named due to its resemblance to the aspergillum, a vessel used for sprinkling holy water. The fruiting bodies, also known as conidial heads, are useful for identifying the different species of Aspergillus fungi, as their fruiting body structures vary depending on the species. 

Aspergillus can live in many places in the environment, including dirt, food, decaying organic matter, grains, and household dust. It grows primarily in damp environments. The fruiting bodies can bud off from the fungus and travel through the air. Once inhaled, Aspergillus may cause disease in humans. However, exposure to the fungus is common, and invasive infections are generally limited to individuals who have an impaired immune system, like people who have undergone an organ transplant or are receiving immunosuppressive treatment (e.g., chronic steroid therapy).

What causes an infection by a fruiting body of Aspergillus?

Fruiting bodies of Aspergillus enter the human host through the respiratory tract, most commonly through the nasal cavity, sinuses, and bronchi of the lungs. The individual’s immune system may react to the foreign substance in the form of an allergic reaction, such as sinusitis, the inflammation of the cavities around the nasal passages. Another example of an allergic reaction is allergic bronchopulmonary aspergillosis (ABPA). ABPA is particularly prevalent in immunocompromised individuals and is characterized by an immune system overreaction to the species Aspergillus fumigatus. 

Fruiting bodies are also found in individuals who have chronic pulmonary aspergillosis, a condition in which the fungus invades the lungs. People are particularly susceptible to chronic pulmonary aspergillosis after having tuberculosis, sarcoidosis, or bronchiectasis. With tuberculosis, the bacteria Mycobacterium tuberculosis attacks the lungs, weakening the immune system and subsequently allowing Aspergillus to invade. Sarcoidosis occurs when inflammatory cells grow within the lungs, so treatment involves medication to suppress the immune system and reduce the amount of inflammation. Unfortunately, suppression of the immune system can make the individual more vulnerable to fungal infections, including with Aspergillus. Lastly, bronchiectasis refers to the condition in which the lungs' airways become damaged, widened, and thickened. This leads to a decline in the body’s ability to clear mucus, and the resulting thickened mucus allows fungal spores to remain in the respiratory tract.  

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How is a fruiting body of Aspergillus diagnosed and treated?

Fruiting body of Aspergillus is diagnosed based on clinical, radiological, and microscopic findings. Clinical findings pointing to immunodeficiency (e.g., recurrent infections in the lungs, ears, and throat) may raise suspicion of Aspergillus infection. Aspergillus infection may also be suspected if one’s occupation involves conditions favorable for fungal growth, such as jobs in the agriculture industry. 

Microbiological isolation by culture is required for confirmation of infection, but this can be difficult. If isolated, the spores can be characterized by length, width, size, and color. Additionally, because the fruiting bodies tend to group together in chains, like pearls on a string, the length of the chains of the conidia can also be a useful characteristic to note. 

A galactomannan (GM) test is another tool for early diagnosis of Aspergillus in high-risk patients, including those who are immunocompromised. GM is an antigen in the cell walls of Aspergillus that can travel from the spores into the infected individual’s blood. Drawing the individual’s blood to look for the presence of the antigen can aid in diagnosis. 

It is important to rule out contamination when determining if a case is due to Aspergillus, as many other environmental yeast and bacteria may present with similar symptoms. To avoid contamination, initiating proper sterile procedure when drawing and processing the blood in the laboratory is imperative.

Treatment of infections from a fruiting body of Aspergillus depends on whether the  infected individual is experiencing symptoms. If the individual is not experiencing any symptoms, the infection can be considered mild and monitored via chest X-ray for improvement. If the individual’s condition worsens, or the aspergillosis infection spreads rapidly from the lungs to other organs (i.e., invasive pulmonary aspergillosis), administration of intravenous antifungal medications, such as voriconazole or amphotericin B, may be required. Kidney and liver damage are potential side effects of these medications, so individuals taking them should have their kidney and liver functions routinely monitored. 

Other treatments, specifically for allergic bronchopulmonary aspergillosis, include oral corticosteroids, which help target inflammation in the airways, and combination corticosteroid-antifungal therapy, which aid in improving overall lung function. If the fungus grows into a clump, known as an aspergilloma, antifungal medications may not be able to penetrate the mass, and surgery may be required to remove the infection. 

What are the most important facts to know about a fruiting body of Aspergillus?

A fruiting body of Aspergillus is the cluster of spores formed by the Aspergillus fungus. The fruiting bodies, also known as conidial heads, are useful for identifying the different species of Aspergillus fungi, as their structures vary depending on the species. The spores are transmitted through the air and can result in allergic bronchopulmonary aspergillosis or other diseases, particularly in those who are immunocompromised. Diagnosis of the fungal infection is achieved by reviewing a thorough clinical history, as well as isolating and culturing the species and using microscopy to confirm. Treatment includes medications, such as antifungals and corticosteroids, and if the infection is severe, surgery may be required. 

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