Mucormycetes are a diverse group of molds, which are a type of fungi. These organisms are commonly found in natural environments around the world. While many people encounter mucormycetes daily without issue, they can cause serious infections in certain individuals.
Understanding Mucormycetes
Mucormycetes are molds belonging to the order Mucorales, with common types including Rhizopus, Mucor, Cunninghamella, Apophysomyces, and Lichtheimia. These fungi are characterized by broad, ribbon-like hyphae with few internal divisions, called septa. They can grow in a wide range of temperatures, with some species thriving at temperatures up to 58°C, and others growing well at human body temperature of 37°C.
These molds are ubiquitous in nature, found almost everywhere. Their natural habitat includes soil, decaying organic matter like leaves, compost piles, and rotten wood, as well as in the air. They are also present in animal dung and can contaminate food if not properly washed. Their spores are widely distributed in both indoor and outdoor environments.
Mucormycosis The Disease
Mucormycetes can cause a rare but severe fungal infection known as mucormycosis, formerly referred to as zygomycosis. This infection is not contagious and cannot spread from person to person or between people and animals. Infection occurs when spores from the environment are inhaled, ingested, or enter the body through a break in the skin.
The primary risk factors for developing mucormycosis are conditions that weaken the immune system. Individuals with uncontrolled diabetes are at a higher risk. Other significant risk factors include cancer, low white blood cell counts (neutropenia), and having too much iron in the body (iron overload or hemochromatosis). Patients who have received organ or stem cell transplants, those on prolonged corticosteroid therapy, or individuals with severe COVID-19 are also more susceptible. Trauma, burns, or surgical wounds can also increase the risk of skin infections.
Forms of Mucormycosis
Mucormycosis can manifest in different forms depending on the site of infection:
Rhinocerebral mucormycosis: Affects the sinuses, eyes, and brain. It is the most common type, especially in people with poorly managed diabetes. Symptoms include one-sided facial swelling, headache, sinus pain, nasal congestion, and potentially black lesions on the nasal bridge or inside the mouth.
Pulmonary mucormycosis: A lung infection often seen in individuals with blood cancers or those who have undergone stem cell transplants. It presents with fever, cough, and chest pain.
Cutaneous mucormycosis: Develops when spores enter through a skin injury, such as a scrape or burn. It leads to painful blisters, ulcers, or discolored skin that may turn black.
Gastrointestinal mucormycosis: Less common, often seen in premature infants or adults with neutropenia. It results from ingesting contaminated food or substances, causing abdominal pain, nausea, vomiting, and sometimes gastrointestinal bleeding.
Disseminated mucormycosis: Occurs when the infection spreads throughout the body, commonly to the brain, but can also affect the spleen, heart, or other organs.
Diagnosis and Treatment
Diagnosing mucormycosis involves a combination of clinical assessment and laboratory tests. Healthcare providers often suspect the infection based on a patient’s medical history, risk factors, and observed symptoms. To confirm the diagnosis, samples of affected fluids or tissues, such as lung fluid, nasal discharge, or a tissue biopsy, are collected for laboratory analysis.
Laboratory scientists examine these samples under a microscope to identify the presence of mucormycetes, which appear as large, non-septate hyphae with irregular diameters. While cultures can be performed, they may sometimes yield negative results even when fungi are visible in tissues. Imaging techniques, such as CT or MRI scans, are also used to assess the extent of the infection and determine if it has spread to other body parts, like the eyes, brain, or lungs.
Treatment for mucormycosis requires aggressive intervention. The mainstays of treatment include antifungal medications, administered intravenously. Amphotericin B is considered a primary therapy. Posaconazole and isavuconazole are also used, and can be given orally or intravenously.
In many cases, surgical removal of infected and necrotic tissue is also necessary to control the spread of the fungus and improve outcomes. This surgical debridement is often aggressive to eliminate the affected tissue. Managing underlying health conditions, such as bringing blood sugar levels under control in diabetic patients or discontinuing immunosuppressive agents when feasible, is also part of comprehensive treatment.
Prevention Strategies
While completely avoiding mucormycetes may not be possible due to their widespread presence, individuals at higher risk can take measures to reduce their exposure. It is advisable to avoid areas with significant dust, such as construction or excavation sites. If these environments cannot be avoided, wearing an N95 respirator mask can help filter out fungal spores.
Protecting the skin is important; wearing shoes, long pants, and long-sleeved shirts during outdoor activities like gardening or yard work can reduce direct contact with soil, moss, or manure. Wearing gloves when handling these materials is recommended. Any skin injuries, cuts, or scrapes should be thoroughly cleaned with soap and water, especially if they have been exposed to soil or dust.
Managing underlying health conditions, such as maintaining good blood sugar control for individuals with diabetes, can also help reduce susceptibility. In some high-risk patients, healthcare providers may consider prescribing antifungal medications as a preventive measure.