22.4 Respiratory Mycoses
3 min read•june 18, 2024
Respiratory mycoses are fungal infections that target the lungs and airways. These infections, caused by pathogens like and Cryptococcus, can range from mild to severe, especially in people with weakened immune systems.
Each fungal infection has unique symptoms and treatments. While some respond well to antifungal drugs, others can be tricky to manage. Fungi use clever tricks to evade our immune system, making these infections a serious concern in healthcare.
Respiratory Mycoses
Common respiratory fungi pathogens
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- Aspergillus species cause a range of respiratory infections ()
- A. fumigatus most common cause of invasive in immunocompromised patients
- A. flavus produces aflatoxins and can cause allergic reactions (sinusitis, bronchopulmonary aspergillosis)
- A. niger rarely pathogenic but can cause ear infections (otomycosis) and pneumonia in immunocompromised individuals
- A. terreus intrinsically resistant to , making treatment challenging
- encapsulated yeast causes , primarily affecting the lungs and central nervous system ()
- opportunistic fungus causes pneumonia (PCP) in immunocompromised patients, particularly those with AIDS
- dimorphic fungus causes , a systemic infection that primarily affects the lungs
- and C. posadasii cause (), a respiratory infection endemic to the southwestern United States (Arizona, California)
- dimorphic fungus causes , which can lead to pulmonary infections and skin lesions
- dimorphic fungus causes , primarily affecting the skin (lymphocutaneous form) but can also cause pulmonary infections
Fungal respiratory diseases comparison
- Aspergillosis
- Symptoms: fever, cough, chest pain, shortness of breath, hemoptysis (coughing up blood)
- Treatment: antifungal drugs ( first-line therapy, , for severe cases)
-
- Symptoms: headache, fever, cough, shortness of breath, skin lesions (cryptococcomas)
- Treatment: antifungal drugs ( for mild-to-moderate cases, amphotericin B plus for severe cases)
- (PCP)
- Symptoms: dry cough, progressive dyspnea (difficulty breathing), fever, chills, fatigue
- Treatment: antibiotics ( first-line therapy, alternative for sulfa-allergic patients)
-
- Symptoms: fever, chills, headache, dry cough, chest pain, fatigue (flu-like symptoms)
- Treatment: antifungal drugs ( for mild-to-moderate cases, amphotericin B for severe cases)
- (Valley Fever)
- Symptoms: fever, cough, chest pain, fatigue, skin rash (erythema nodosum), joint pain (desert rheumatism)
- Treatment: antifungal drugs ( for mild-to-moderate cases, itraconazole or amphotericin B for severe cases)
-
- Symptoms: fever, cough, chest pain, weight loss, skin lesions (verrucous or ulcerative)
- Treatment: antifungal drugs (itraconazole for mild-to-moderate cases, fluconazole or amphotericin B for severe cases)
- Sporotrichosis
- Symptoms: skin lesions (nodules, ulcers), lymphadenopathy (swollen lymph nodes), pulmonary nodules
- Treatment: antifungal drugs (itraconazole for lymphocutaneous form, fluconazole or for alternative therapy)
Immune evasion by fungal pathogens
- Evasion of innate immune recognition
- Masking of cell wall components () to avoid detection by host receptors ()
- Secretion of immunomodulatory compounds ( by Aspergillus) to suppress immune response
- Resistance to phagocytosis and intracellular killing
- Formation of capsules (Cryptococcus) to prevent phagocytosis by macrophages and neutrophils
- Production of antioxidants (, ) to neutralize reactive oxygen species within phagocytes
- Inhibition of phagolysosome formation and acidification, preventing fungal cell degradation
- Modulation of adaptive immune responses
- Interference with antigen presentation and T cell activation, reducing specific immune responses
- Induction of immunosuppressive cytokines () to dampen overall immune response
- Promotion of (humoral immunity) over protective (cell-mediated immunity)
- Biofilm formation
- Development of biofilms to enhance adherence to host tissues and protect from immune defenses
- Increased resistance to antifungal drugs within biofilms due to extracellular matrix and altered gene expression
Fungal growth and infection mechanisms
- are often the initial infectious particles inhaled into the respiratory tract
- allows for tissue invasion and dissemination in many respiratory mycoses
- enables certain fungi to switch between yeast and hyphal forms, adapting to different host environments
- occur when normally harmless fungi take advantage of a weakened immune system
- Immunocompromised hosts are particularly susceptible to severe and invasive fungal infections
- can develop through various mechanisms, complicating treatment of respiratory mycoses
Key Terms to Review (62)
Amphotericin B: Amphotericin B is an antifungal medication primarily used to treat serious fungal infections. It works by binding to ergosterol in fungal cell membranes, causing cell death.
Amphotericin B: Amphotericin B is a potent antifungal medication used to treat a variety of serious fungal infections. It is a polyene macrolide antibiotic that disrupts the cell membrane of fungal cells, leading to their death or inhibition of growth. Amphotericin B is particularly relevant in the contexts of mechanisms of other antimicrobial drugs, respiratory mycoses, and parasitic infections of the circulatory and lymphatic systems.
Antifungal Resistance: Antifungal resistance refers to the ability of fungal pathogens to withstand or adapt to the effects of antifungal drugs, rendering these medications less effective in treating fungal infections. This phenomenon has significant implications for the management of mycoses, including skin, respiratory, and reproductive system infections.
Aspergillosis: Aspergillosis is an infection caused by the Aspergillus species of fungi, which primarily affects the respiratory system but can disseminate to other organs. It is most commonly seen in immunocompromised individuals.
Aspergillosis: Aspergillosis is a group of infections and allergic reactions caused by a type of fungus called Aspergillus. These infections primarily affect the respiratory system and can range in severity from mild to life-threatening, depending on the individual's immune status and the specific type of Aspergillus infection.
Aspergillus: Aspergillus is a genus of mold commonly found in the environment that can cause infections, particularly in immunocompromised individuals. These fungi are known for producing conidia, which can be inhaled and lead to respiratory issues.
Aspergillus flavus: Aspergillus flavus is a species of fungus that is a common contaminant of agricultural crops and a major cause of respiratory mycoses, particularly in immunocompromised individuals. It is a significant threat to public health due to its ability to produce aflatoxins, potent carcinogenic compounds.
Aspergillus fumigatus: Aspergillus fumigatus is a ubiquitous fungus that can cause a range of respiratory infections, from mild allergic responses to life-threatening invasive disease. It is a key topic in the study of fungi, the anatomy and microbiota of the respiratory tract, as well as respiratory mycoses.
Aspergillus niger: Aspergillus niger is a species of fungus that is commonly found in soil, decaying organic matter, and the environment. It is a significant cause of respiratory mycoses, a group of fungal infections that primarily affect the lungs and respiratory system.
Aspergillus terreus: Aspergillus terreus is a species of fungus that is a common cause of respiratory mycoses, particularly in immunocompromised individuals. It is a filamentous, saprophytic fungus that can cause a range of respiratory infections, including invasive aspergillosis, a serious and potentially life-threatening condition.
Blastomyces dermatitidis: Blastomyces dermatitidis is a dimorphic fungus that is the causative agent of blastomycosis, a serious respiratory mycosis. It is a significant public health concern, particularly in areas where the fungus is endemic, as it can cause severe and potentially life-threatening infections in humans and animals.
Blastomycosis: Blastomycosis is a fungal infection caused by the dimorphic fungus Blastomyces dermatitidis. It primarily affects the lungs but can disseminate to other body parts such as skin and bones.
Blastomycosis: Blastomycosis is a serious fungal infection caused by the dimorphic fungus Blastomyces dermatitidis. It primarily affects the lungs but can also spread to other organs, making it a respiratory mycosis of significant concern.
BSL-3 microbe: A BSL-3 microbe is a pathogen that requires Biosafety Level 3 containment due to its potential to cause serious or potentially lethal disease through inhalation. These microbes necessitate strict laboratory practices and specialized equipment to prevent airborne transmission.
Coccidioides immitis: Coccidioides immitis is a fungus that causes the respiratory disease coccidioidomycosis, also known as Valley Fever. It is a dimorphic fungus that can exist in both a mycelial (filamentous) form and a spherical, endospore-producing form within the human host.
Coccidioides posadasii: Coccidioides posadasii is a dimorphic fungus that is the causative agent of coccidioidomycosis, also known as Valley Fever. It is a significant respiratory mycosis found primarily in the Southwestern United States and parts of Mexico and Central America.
Coccidioidomycosis: Coccidioidomycosis, also known as Valley Fever, is a fungal infection caused by Coccidioides species. It primarily affects the lungs and can cause flu-like symptoms.
Coccidioidomycosis: Coccidioidomycosis, also known as Valley Fever, is a fungal infection caused by the Coccidioides species of fungi. It is primarily a respiratory mycosis that can be transmitted through the inhalation of fungal spores found in certain geographic regions.
Cryptococcosis: Cryptococcosis is a fungal infection caused by Cryptococcus neoformans, commonly affecting the lungs and central nervous system. It often occurs in immunocompromised individuals, such as those with HIV/AIDS.
Cryptococcosis: Cryptococcosis is a serious fungal infection caused by the Cryptococcus neoformans or Cryptococcus gattii fungi. It primarily affects the lungs and central nervous system, and is considered an opportunistic infection that commonly occurs in individuals with weakened immune systems, such as those with HIV/AIDS or organ transplant recipients.
Cryptococcus neoformans: Cryptococcus neoformans is an encapsulated yeast that primarily causes infections in immunocompromised individuals. It is notable for causing severe respiratory and central nervous system infections.
Dectin-1: Dectin-1 is a pattern recognition receptor (PRR) expressed on the surface of certain immune cells, particularly macrophages and dendritic cells. It plays a crucial role in the recognition and response to fungal pathogens, serving as a key component in the innate immune system's defense against respiratory mycoses.
Dimorphism: Dimorphism refers to the ability of certain organisms, such as fungi and some pathogens, to exist in two distinct forms or phases. This versatility allows these organisms to adapt to different environmental conditions and host interactions, often contributing to their virulence and pathogenicity.
Fluconazole: Fluconazole is an antifungal medication used to treat various fungal infections. It works by inhibiting the synthesis of ergosterol, an essential component of fungal cell membranes.
Fluconazole: Fluconazole is an antifungal medication used to treat a variety of fungal infections. It works by interfering with the fungal cell membrane, disrupting the fungal cell's ability to maintain its structure and function, ultimately leading to the death of the fungal cells.
Flucytosine: Flucytosine is an antifungal medication used to treat serious fungal infections. It works by inhibiting fungal DNA and RNA synthesis.
Flucytosine: Flucytosine is a synthetic fluorinated pyrimidine antifungal agent used to treat various fungal infections, particularly those caused by Candida and Cryptococcus species. It acts by interfering with fungal cell division and DNA synthesis, making it an important tool in the management of respiratory mycoses.
Fungal Spores: Fungal spores are the reproductive units of fungi that are dispersed to facilitate the spread and propagation of the fungal species. These microscopic, resilient structures are essential for the survival and dissemination of fungi in various environments, including those relevant to the topic of Respiratory Mycoses.
Giemsa staining: Giemsa staining is a histological stain used for the visualization of cellular components, particularly useful in identifying parasites and differential white blood cells. It is commonly employed in microbiology to diagnose infections by staining organisms such as fungi and protozoa.
Gliotoxin: Gliotoxin is a secondary metabolite produced by certain fungi, particularly Aspergillus fumigatus, that is known for its immunosuppressive and cytotoxic properties. This term is important in the context of respiratory mycoses, as gliotoxin is a key virulence factor associated with invasive aspergillosis, a severe fungal infection of the lungs.
Granulomatous lesions: Granulomatous lesions are localized nodular inflammations formed by a collection of immune cells, primarily macrophages, which occur in response to chronic infection or inflammation. These lesions often form to contain pathogens that are difficult to eradicate.
Histoplasma capsulatum: Histoplasma capsulatum is a dimorphic fungus that is the causative agent of histoplasmosis, a respiratory mycosis. It is a thermally dimorphic fungus, meaning it exhibits different forms at different temperatures - a mycelial form at cooler temperatures and a yeast form at warmer temperatures within the human body.
Histoplasmosis: Histoplasmosis is a respiratory infection caused by the inhalation of spores from the fungus Histoplasma capsulatum. It primarily affects the lungs but can disseminate to other organs in immunocompromised individuals.
Histoplasmosis: Histoplasmosis is a fungal infection caused by the inhalation of spores from the fungus Histoplasma capsulatum. It primarily affects the lungs and is considered a respiratory mycosis, a group of fungal infections that target the respiratory system.
Hyphal Growth: Hyphal growth refers to the elongation and branching of hyphae, which are the filamentous structures that make up the body of a fungus. This mode of growth is a defining characteristic of fungi and is crucial for their survival, reproduction, and pathogenesis in the context of respiratory mycoses.
IL-10: IL-10, or Interleukin-10, is a cytokine that plays a crucial role in regulating the immune system. It is primarily produced by regulatory T cells and acts to suppress inflammatory responses, promoting immune tolerance and preventing autoimmune disorders.
Immunocompromised Host: An immunocompromised host is an individual whose immune system is impaired or weakened, making them more susceptible to infections and diseases. This term is particularly relevant in the context of respiratory mycoses, as these individuals are at a higher risk of developing severe and potentially life-threatening fungal infections.
Itraconazole: Itraconazole is an antifungal medication used to treat a variety of fungal infections. It is particularly effective against dermatophytes, yeasts, and molds.
Itraconazole: Itraconazole is a broad-spectrum triazole antifungal drug used to treat a variety of fungal infections, including those affecting the skin, nails, and respiratory system. It works by disrupting the fungal cell membrane, inhibiting the synthesis of ergosterol, a critical component of the fungal cell wall.
Ketoconazole: Ketoconazole is an antifungal medication used to treat a variety of fungal infections, including those that affect the skin and respiratory system. It works by inhibiting the synthesis of ergosterol, an essential component of fungal cell membranes.
Melanin: Melanin is a natural pigment produced by specialized cells called melanocytes. It is responsible for the color of skin, hair, and eyes, and also plays a crucial role in protecting the skin from the harmful effects of ultraviolet (UV) radiation from the sun.
Meningitis: Meningitis is an inflammation of the protective membranes covering the brain and spinal cord, known as the meninges. It can be caused by bacterial, viral, fungal, or parasitic infections.
Mucor: Mucor is a genus of fungi commonly found in soil, decaying organic matter, and sometimes in human respiratory systems. It can cause mucormycosis, a serious infection particularly affecting immunocompromised individuals.
Mucormycosis: Mucormycosis is a serious fungal infection caused by molds belonging to the Mucorales order. It primarily affects immunocompromised individuals and can manifest in various forms, including pulmonary mucormycosis.
Opportunistic Infections: Opportunistic infections are infections caused by pathogens that normally do not cause disease in individuals with a healthy, functioning immune system, but can take advantage of weakened or compromised immunity to cause illness. These infections are a significant concern in individuals with immunodeficiencies, such as those with HIV/AIDS, cancer, or organ transplants, who are more susceptible to developing these types of infections.
Pentamidine: Pentamidine is a synthetic diamidine compound used as an antiprotozoal and antifungal medication, primarily in the treatment of respiratory mycoses caused by opportunistic fungal infections.
Pneumocystis jirovecii: Pneumocystis jirovecii is an opportunistic fungal pathogen that can cause a severe form of pneumonia, known as Pneumocystis pneumonia (PCP), in individuals with weakened immune systems. This microscopic fungus primarily infects the alveoli, or air sacs, of the lungs, leading to respiratory distress and potentially life-threatening complications.
Pneumocystis pneumonia: Pneumocystis pneumonia is a type of pneumonia caused by the fungus Pneumocystis jirovecii (formerly known as Pneumocystis carinii). It is a common opportunistic infection that primarily affects individuals with weakened immune systems, such as those with HIV/AIDS or undergoing immunosuppressive treatments.
Potassium Iodide: Potassium iodide is a chemical compound composed of potassium and iodide ions. It is a salt that has various applications, including in the treatment of certain medical conditions and as a protective measure against radioactive iodine exposure.
Rhizopus arrhizus (oryzae): Rhizopus arrhizus (oryzae) is a species of fungi known to cause mucormycosis, particularly affecting the respiratory system. It commonly infects immunocompromised individuals and can lead to severe respiratory issues.
Sabouraud's dextrose agar: Sabouraud's dextrose agar is a type of fungal culture medium specifically designed to isolate and cultivate dermatophytes and other types of fungi. It contains peptones, dextrose, and a low pH to inhibit bacterial growth while promoting fungal growth.
Sporothrix schenckii: Sporothrix schenckii is a dimorphic fungus that can cause a rare infection known as sporotrichosis. It is the causative agent of a respiratory mycosis that primarily affects the skin and subcutaneous tissues, but can also disseminate to other organs.
Sporotrichosis: Sporotrichosis is a fungal infection caused by the dimorphic fungus Sporothrix schenckii. It is primarily a subcutaneous mycosis that can manifest in various clinical forms, including cutaneous, lymphocutaneous, and disseminated infections, and is considered a respiratory mycosis due to its ability to be transmitted through inhalation of fungal spores.
Superoxide Dismutase: Superoxide dismutase (SOD) is an enzyme that catalyzes the conversion of the superoxide radical (O2-) into oxygen (O2) and hydrogen peroxide (H2O2), which are less reactive species. It is a crucial antioxidant defense mechanism that helps protect cells from oxidative stress and damage caused by free radicals.
Th1 Response: The Th1 response is a type of adaptive immune response that is primarily focused on the elimination of intracellular pathogens, such as viruses and certain bacteria. It is characterized by the activation of T helper 1 (Th1) cells, which produce specific cytokines that coordinate the body's defense against these types of infections.
Th2 Response: The Th2 response is a type of adaptive immune response primarily mediated by T helper 2 (Th2) cells. It is characterized by the production of specific cytokines and the activation of certain immune cells, playing a crucial role in the body's defense against parasitic infections and the development of allergic reactions.
Trimethoprim-sulfamethoxazole: Trimethoprim-sulfamethoxazole is a combination antibiotic used to treat a variety of bacterial infections. It inhibits successive steps in the bacterial folate synthesis pathway, making it particularly effective against certain strains.
Trimethoprim-sulfamethoxazole: Trimethoprim-sulfamethoxazole, also known as co-trimoxazole, is a combination antibiotic medication used to treat a variety of bacterial infections. It consists of two active ingredients, trimethoprim and sulfamethoxazole, which work synergistically to inhibit bacterial growth and proliferation.
Valley Fever: Valley Fever, also known as coccidioidomycosis, is a fungal infection caused by the Coccidioides species of fungi. It is primarily a respiratory mycosis that affects the lungs and can lead to a range of symptoms, from mild flu-like illness to severe pneumonia and disseminated disease.
Voriconazole: Voriconazole is an antifungal medication used to treat serious fungal infections, including those caused by Aspergillus and Candida species. It works by inhibiting the synthesis of ergosterol, a key component of fungal cell membranes.
Voriconazole: Voriconazole is a broad-spectrum triazole antifungal medication used to treat a variety of fungal infections, including those caused by Aspergillus and Candida species. It is particularly effective in the management of respiratory mycoses and acts by inhibiting the fungal enzyme lanosterol 14α-demethylase, which is crucial for the synthesis of ergosterol, a key component of the fungal cell membrane.
β-glucans: β-glucans are a type of polysaccharide found in the cell walls of fungi, bacteria, and certain plants. They are known for their immunomodulatory properties and have been studied extensively in the context of respiratory mycoses, which are fungal infections of the respiratory system.