Fruiting Body of Aspergillus · What Is It, Treatment, and More

A fruiting body of Aspergillus refers to the cluster of spores produced by the species of 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, 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. Like other types of fungus, it grows primarily in damp environments. The spores from 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). 

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 this foreign substance in the form of an allergic reaction, causing sinusitis, or 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 individuals with underlying lung disease, particularly asthma and cystic fibrosis, and is characterized by an immune system overreaction to the species Aspergillus fumigatus.  

Aspergillus can also cause chronic infections affecting the lung tissue, especially in people with pre-existing lung conditions like 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 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.   

In addition to the lungs, Aspergillus can also grow in wounds on the surface of the skin, such as surgical cuts and burns, leading to soft tissue infections.  

Fruiting body of Aspergillus is diagnosed based on clinical, radiological, laboratory and microscopic findings. Clinical findings pointing to immunodeficiency (e.g., recurrent infections in the lungs, ears, and throat) may raise suspicion of Aspergillus infection, especially if they’re accompanied by symptoms like a persistent cough, coughing up blood, shortness of breath, and weight loss. Aspergillus infection may also be suspected if one’s occupation involves conditions favorable for fungal growth, such as jobs in the agriculture industry (e.g., farmers, gardeners, compost facility employees, or construction and demolition workers handling old buildings).  

In individuals with suspected pulmonary aspergillosis, a CT scan of the lungs may be performed to look for evidence of the fungus. In invasive pulmonary aspergillosis, particularly in immunocompromised patients, CT often shows nodules with a surrounding ground-glass halo (the “halo sign”) in early stages, reflecting hemorrhagic infarction. In chronic pulmonary aspergillosis, imaging may reveal thick-walled cavities, often in the upper lobes, and associated pleural thickening from long-standing infection and scarring of the lung tissue. 

Microbiological isolation by culture is required for confirmation of infection, but this can be difficult. Samples are often obtained via a sputum sample or bronchoalveolar lavage (BAL), a diagnostic procedure used to collect fluid from the lower airways using a bronchoscope. If isolated, the spores can be characterized by length, width, size, and color, which aids in determining the species of fungus. Additionally, because the fruiting bodies tend to group together in chains, like pearls on a string, the length of the chains of the conidial heads 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. Detecting this antigen in the individual’s blood can aid in diagnosis of invasive aspergillosis.  

Treatment of infections from a fruiting body of Aspergillus depends on whether the  infection is causing any symptoms. If the individual is asymptomatic, the infection can be considered mild and monitored for improvement. If the individual’s condition worsens, or the aspergillosis infection spreads 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.