L31: Fungal Infections of the Respiratory Tract Flashcards
Zygomycoses (mucormycosis)
Group of uncommon but potentially fatal infection caused by fungi belonging to Zygomycetes class; infection rare in normal healthy individuals but can occur in people with immunosuppression, diabetes, or burns
3 main genera of zygomycetes
- Rhizopus
- Absidia
- Mucor
- -All have non-septate hyphae
Rhinocerebral zygomycosis
Most common form of zygomycosis, primarily diabetic patients, originates in sinuses
Where else can zygomycotic infections occur?
Zygomycotic infections of the lungs, skin and GI tract can occur in immunosuppressed or burn patients
Diagnosis of zygomycoses
In tissue section, broad aseptate hyphae are frequently observed branching at right angles
Treatment of zygomycoses
Amphotericin B
What causes candidiasis?
Yeast of the genus Candida (mostly Candida albicans)
Candida albicans
Considered normal flora and present in environment, exists in yeast, pseudohyphal, and hyphal forms
Oral candidasis (thrush)
Seen in infants, adults after steroids/antibiotics, AIDS patients
How does thrush present?
Diffuse erythema and white cheesy patches on the surface of the buccal mucosa, throat, tongue, and gums; plaques can be scraped or wiped away revealing lesion
Diagnosis of thrush
Direct observation of Candida in clinical material (generally don’t need cultures)
Treatment of thrush
Oral formulations (mouth washes or lozenges) of nystatin and azole compounds
Basic info about systemic mycoses
ALL present initially as pulmonary infection – diverse group of presentations, not opportunistic, found in environment, acquired by inhalation of fungal elements
Systemic mycoses that are dimorphic fungi (4 types)
Histoplasma capsulatum, Blastomyces dermatitidis, Paracoccidioides brasiliensis, Coccidioides immitis
Systemic mycoses that is encapsulated yeast
Cryptococcus neoformans (also has a worldwide distribution)
Regional trends of histoplasmosis
Most prevalent in distinct regions of North/Central America, endemic in Mississippi and Ohio River valleys
Cause of histoplasmosis
Histoplasma capsulatum; found in soil under humid climate conditions, infection acquired by inhalation of micro- or macroconidia from environment
Histoplasmosis transmission
From bird/bat droppings, gets inhaled and can survive in macrophages (converts to yeast form and replicates there) – normally immune system takes care of it on its own
Pulmonary histoplasmosis
Mild flu-like illness with dry cough, fever, fatigue – can sometimes cause small calcifications on CXR
Chronic pulmonary and disseminated histoplasmosis
Typically occur in immunocompromised individuals – experience fever, night sweats, anorexia, weight loss, fatigue and respiratory symptoms – also hepatomegaly, splenomegaly, and lymphadenopathy
Diagnosis of histoplasmosis
Direct observation of organisms (yeast form) in tissues or clinical samples, cultivation of organisms from clinical samples, serology (detected Ag or Ab)
Treatment of histoplasmosis
Amphotericin B (but AIDS patients/immunosuppressed individuals need lifelong suppressive therapy with azoles)
Regional trends of blastomycosis
Endemic in Ohio and Mississippi river valley and a little bit in Missouri and Arkansas river basins
Cause of blastomycosis
Blastomyces dermatitidis (very large with very thick cell walls)
Disease process of blastomycosis
Pulmonary disease with potential to disseminate, acquired through inhalation of spores from environment, normally asymptomatic
Symptoms of acute blastomycosis
Cough, fever, chills, arthralgia, myalgia (may also mimic bacterial pneumonia with chest pain and sputum)
Symptoms of chronic pulmonary blastomycosis
Cough, fever, night sweats, weight loss, sputum production (mimics TB)
Symptoms of disseminated disease
Skin lesions and bone infections – must be treated
Diagnosis of blastomycosis
Observation of distinct yeast forms in sputum or biopsy material
Treatment of blastomycosis
Amphotericin B, azoles for uncomplicated pulmonary disease (if treated at all)
Regional trends of paracoccidioidomycosis
Limited to tropical regions of South and Central America (90% of disease occurs in men)
Cause of paracoccidioidomycosis
Paracoccidioides brasiliensis; forms ship’s wheel or Mickey Mouse ears
Disease process of paracoccidioidomycosis
Most infections asymptomatic, pulmonary infection and disseminated disease possible
Diagnosis of paracoccidioidomycosis
Observation, cultivation, and serology
Regional trends of coccidioidomycosis
Throughout Western hemisphere, highly endemic in San Joaquin Valley (CA) and southern Arizona – follow drought-rain-drought pattern
Life cycle of coccidioidomycosis
Arthrocanidia (big hyphae) break in pieces and blow around; once inside forms spherules (look like bags of yeast) inside body
Disease process of coccidioidomycosis
Most individuals asymptomatic, pulmonary disease can be mild to moderate influenza-like syndrome – normally spontaneously resolves
Disseminated disease in coccidioidomycosis
Rare, develops within one year of infection, infects bones, joints, skin, and CNS (“desert rheumatism”)
Coccidial meningitis
Develops slowly with increasing headache, fever, stiff neck, and other neurological signs
Diagnosis of coccidioidomycosis
Observation (spherule!), cultivation, serology
Treatment of coccidioidomycosis
Azole or Amphotericin B
Cryptococcosis basics
Found throughout the world, leading form of fungal meningitis
Cause of cryptococcosis
Cryptococcus neoformans (NOT DIMORPHIC, encapsulated yeast), can be isolated from environment – comes from pigeon/bird droppings
Fungal meningitis
Most commonly recognized form of cryptococcal infection, develops slowly and causes intermittent bouts of headache, irritability, dizziness and other CNS – life-threatening (common in AIDS patients)
Diagnosis of cryptococcosis
India ink stain, cultivation, serology
Pneumocystis jiroveci (carinii) pneumonia (PCP)
Highly lethal, occurs mostly in immunocompromised (AIDS)
P. jiroveci
Eukaryotic organism, related to fungi – not much known about it
Presentation of PCP
Initiated through inhalation of cysts, asymptomatic infection in healthy individuals but when symptomatic = dyspnea, nonproductive cough, fever
Diagnosis of PCP
Identification of organisms (trophozoite, sporozoites, cysts) in clinical material
Basics of aspergillosis
Aspergillus (many diff. species), rarely pathogenic in normal individual, wide range of clinical disease in immunocompromised individuals
2 main fungal causes of aspergillosis
A. fumigatus and A. flavus – not dimorphic, septic hyphae that grow inside our tissues
Acute pulmonary infection (aspergillosis)
Colonization of pre-existing lung lesions with “fungus balls” that are typically unilateral and asymptomatic
Invasive/disseminated/systemic infection
Occurs primarily in leukemia, neutropenia, or organ/marrow transplant patients, often fatal if not detected
