Exam #4: Fungal Infections of the Respiratory Tract Flashcards
What is Zygomycosis (Mucromycosis)?
A class of diseases caused by infection of fungi belonging to the class, "Zygomycetes" - Found in: soil, decaying vegetation, and food
What species of Zygomycetes cause Zygomycosis?
1) Rhizopus
2) Absidia
3) Mucor
What are the predisposing factors to zygomyces infection?
- Immunosuppression
- DM
- Burns
*Infection in a normal, healthy individual is rare
What are the characteristics of the zygomycetes?
- Non-septate hyphae
- Reproduce sexually to produce spores
Describe the common clinical presentation & pathogenesis of rhinocerebral zygomycosis.
- Primarily occurs in Diabetic patients
- Infection originates in sinuses, following inhalation of spores
- Spreads to neighboring tissues
Essentially, infection begins as a typical sinus infection but then progresses to facial/ periorbital edema, visual disturbances, altered mental status, coma, & death as the infection spread to tissues surrounding the sinuses.
Aside from the sinuses, where else can there be zygomycotic infections?
- Skin via traumatic inoculation
- GI (neonates & premature infants)
How is zygomycosis diagnosed? Morphologically what is the key feature that you’re looking for?
- Observation of hyphal elements
- Culture confirmation
Broad aseptate hyphae in blood vessels frequently branching at 90 degree angles
How is zygomycosis treated?
Amphotericin B
What species of candidia causes most candidiasis infections?
C. albicans
Note that this is considered to be part of the normal flora
Candidia is dimorphic. Which form is present in the normal flora & which form is typically pathogenic?
Normal= yeast
Pathogenic= mold/ hyphae
What is Thrush? What are the symptoms/ presentation?
- Oral Candidiasis infection
- Diffuse erythema with white patches (cheesy) on the surface of the buccal mucosa, throat, tongue, & gums
What patient populations are susceptible to Thrush?
- Infants
- Adults undergoing treatment with: steroids, antineoplastic drugs, antibiotics
- AIDS patients
How is oral candidiasis diagnosed?
Direct observation of candidia in clinical material
*Note that culture is typically not necessary; candidia is part of the normal flora (yeast); therefore, it is difficult to distinguish between colonization & infection.
How is oral candidiasis treated?
Oral formulations of nystatin & azole compounds i.e. mouthwash or lozenges
What patient populations most frequently get an esophagitis?
AIDS/ HIV
*Extension of thrush/ oral candidiasis into the esophagus
What are systemic mycoses?
- Diverse group of fungal infections that initally infect the lungs & then lead to systemic infection
- All originate as an inhaled pathogen
- Occur in BOTH healthy and immunosuppressed individuals
What five fungi are considered “systemic mycoses?”
1) Histoplasma capsulatum
2) Blastomyces dermatitidis
3) Paracoccidioides brasiliensis
4) Coccidioides immits
5) Crytococcus neoformans
Which of the systemic mycoses are dimorphic? What forms are they in in the enviornment & in human?
1) Histoplasma capsulatum
2) Blastomyces dermatitidis
3) Paracoccidioides brasiliensis
4) Coccidioides immits
*Exist as MOLD in environment, & YEAST in human infection, which is opposite of candidia
What is cryptococcus neoformans?
Crytococcus neoformans is an encapsulated yeast
Where is histoplasma capsulatum geographically most prevalent?
- North & Central America
- In the U.S, specifically in the Mississippi & Ohio River Valley
What causes histoplasmosis?
Histoplasma capsulatum
Note that this disease is also known as “Darling’s Disease, Cave Dweller’s Disease, & Spelunker’s Disease”
What form of histoplasma capsulatum is present in the environment? What causes infection?
- Mold that is commonly found in soil containing bird & bat droppings
- Infection is acquired by inhalation of micro or macroconidia
*95% of exposed individuals are asymptomatic
Describe the pathogenesis of histoplasmosis.
- Inhaled fungal spores are phagocytosed by pulmonary macrophages & convert into the YEAST form
- Organism survives and replicates within macrophages causing “pulmonary histoplasmosis.”
- Progression from that state can be to chronic pulmonary histoplasmosis or disseminated histoplasmosis, both of which are more common in immunosuppressed individuals
What are the symptoms of pulmonary histoplasmosis?
Dry cough
Fever
Fatigue
How is pulmonary histoplasmosis treated?
- Most infections resolve without any intervention
- Calcification of pulmonary lesions due to cell mediated immunity & macrophage activation
What are the symptoms of disseminated histoplasmosis?
- Fever
- Night sweats
- Anorexia
- Weight loss
- Fatigue
+ Respiratory symptoms
How is histoplasmosis diagnosed?
1) Direct observation of organisms in tissues or clinical samples
2) Cultivation of organisms from clinical samples
3) Serological testing
*A combination of these approaches is commonly employed
How is histoplasmosis treated?
Amphotericin B
*AIDS patients and other immunosuppresssed individuals often require lifelong suppressive therapy to prevent relapse (with azoles)
What organism causes Blastomycosis
Blastomyces Dermatitidis
Where is Blastomyces Dermatitidis geographically most prevalent?
1) Ohio & Mississippi River Valley (like histoplasma capsulatum)
2) AND, to a lesser extend, the Arkansas River Basin
How is Blastomyces dermatitidis differentiated from Histoplasma?
Larger size & very thick cell wall present in Blastomyces
How does pulmonary blastomycosis present?
Like Histoplasmosis with a mild flu-like illness, as bacterial pneumoni, or as TB:
- Cough, BUT with frank sputum production
- Fever
- Fatigue
How does disseminated Blastomycosis present?
Ulcerative lesions of the skin, bone, and urogenital tract
- Skin lesions are ulcerative & disfiguring (painless)
- Bone necrosis & granuloma formation
- Prostate involvement
How is blastomycosis diagnosed?
Observation of distinct yeast form in sputum or biopsy
How is blastomycosis treated?
Amphotericin B is the gold standard
Note that Fluconazole & other azole compounds have shown promise in uncomplicated pulmonary disease
What organism causes Paracoccidioidomycosis?
Paracoccidioides barasiliensis
Where is paracoccidioides barasiliensis geographically most prevalent? Is it more common in men or women?
- Most prevalent in South America
- 90% of the disease occurs in men; appears estrogen may inhibit growth
How does paracoccidiodomycosis present?
- Most infections as asymptomatic
- Primary pulmonary infection is similar to histoplasmosis & blastomycosis
- Disseminated disease typically presents as chronic cutaneous & mucocutaneous ulcers
How is paracoccidiodomycosis diagnosed?
- Direct observation of morphology
- Large yeast covered with multiple buds
- Takes on a “ship’s wheel” or “Mickey mouse ears” appearance
What is the most common systemic fungal infection seen in the US? Where is it most geographically prevalent?
- Coccidiodomycosis
- San Joaquin Valley
*Must be reported & typically
follows a drought-rain-drought cycle that results in large numbers of fungal elements in blowing dust
What are the distinguishing features of coccidiodomycosis?
Spherule, which is a multinucleated structure that undergoes several internal divisions to produce hundreds of single nucleated spores
What are the symptoms of coccidiodomycosis?
- Most infected individuals are asymptomatic
- Remainder develop flu-like symptoms
- A small number of those will later develop progressive chronic pulmonary disease with cavity formation
What is the presentation of disseminated coccidioiomycosis?
- Desert rheumatism, which is a triad of symptoms including: fever, skin nodules, & joint pain
- Coccidial meningitis (lesser of the two causes of fungal meningitis)
What is the leading cause of fungal meningitis?
Cryptococcus neoformans
How is crytococcus neoformans different from the other systemic fungi?
NOT Dimorphic; rather, it is an encapsulated yeast
Where is cryptococcus present?
Bird droppings (mostly pigeon)
How does fungal meningitis differ from bacterial meningitis?
Fungal= slow onset vs. bacterial fast onset
How is cryptococcus diagnosed?
India Ink
How is cryptococcus meningitis treated?
- Long term Amphotericin B & 5-Fluorcytosine (6-10 weeks)
- AIDS patients may require suppressive therapy
What is pneumocystis carinii pneumonia (PCP)?
The causative agent of a highly lethal form of pneumonia that develops in immunocompromised patients (AIDS)
Describe the pathogenesis of PCP.
- Single celled eukaryotic organism with simlarities to protozoa
- Exists in a cyst and trophozoites form
- Infection is initiated by inhalation of the cyst form
What is the clinical presentation of PCP?
- Dyspnea
- Nonproductive cough
- Fever
How is PCP diagnosed?
Identification of organisms in clinical material through specialized staining techniques
How is PCP treated?
Trimethoprim-sulfamethoxazole compounds that interfere with folate synthesis
What species of aspergillus are most commonly associated with disease?
A. fumigatus & A. flavus
Describe the pathogenesis of aspergillus.
- Aspergillus exists in the environment as a mold that releases conidia that are aerosolized
- Conidia are inhaled and infect existing lung lesions
- Hyphal growth in tissue causes disease pathology
What is an aspergilloma?
- Fungus ball that infections a pre-existing lung lesion
How do aspergillomas present on CXR?
Space-occupying lesions that move as the patient changes position
How is aspergillus diagnosed?
- Hyphae observed in clinical sample
- Appear as V-shaped branches at a 45 degree angle in blood vessels
How is aspergillosis treated?
- Newer classes of azoles
- Echinocandin
- Amphotericin B
*Surgical removal of aspergillomas is common
