Mycology Flashcards
Systemic mycoses
- All of them Can cause pneumonia and can disseminate
- They are dimorphic fungi: cold (20C)= mold, heat (37C) = yeast
- Treatment: fluconazole or itraconazole for local infection; amphotericin B for systemic infection.
- Can form granulomas (like TB) but cannot be transmitted person to person (unlike TB)
- Causal agents:
- Histoplasma : histoplasmosis
- Blastomycosis: Balstomyces dermatitidis
- Coccidioidomycosis: coccidioides
- Paracoccidioidomycosis: paraccoccidio
- Dx: sputum cytology and culture on blood agar and sabouraud mold agar.
Histoplasmosis
Histoplasma capsulatum
*Endemic region: eastern Great Lakes, Ohio, Mississippi River and Missouri River.
* exposure to bird or bat (murcielago) excrement
* Facultative intracellular yeast
* Disease: Fungus Flu (pneumonia) normal patients with acute pulmonary; inmunocompromised patient with chronic pulmonary or disseminated infection.
Lesions have the tendency to calcify as they heal.
Disseminated infection: mucocutaneous lesions are common.
Dx: sputum or blood cultures with mononuclear cells pack with yeast cells.
Tx: itraconazole for mild, amphotericin B for severe.
Coccidioidomycosis
Coccidioides immitis
*Dimorphic fungus:
-environmental form: hyphae breaking up in arthroconidia.
Found in desert sand: Southwestern United States California especially San Joaquin Valley, Arizona, Texas, Nevada.
-Tissue form: spherules with endospores which we can see in the sputum .
*Disease: Valley Fever: asymptomatic to self-resolving pneumonia or erythema nodosum
Blastomycosis
Blastomyces dermatitidis
Endemic regions: north and South Carolina, co exist with histoplasmosis
Disease:
-Acute and chronic pulmonary disease
-Disseminated to skin
Dx: Sputum has broad based, budding yeast with double, refractive cell walls
Paracoccidioidomycosis
LATIN AMERICA systemic mycoses
budding yeasts with “captain’s wheel” formation
Cutaneous mycoses
Tinea (dermatophytes)
- Tinea (dermatophytes) : Microsporum, Trichophyton, Epidemophyton. They are branching septate hyphae visible on KOH preparation with blue fungal stain. The lesions are itching.
- Tinea capitis: head, scalp. Associated with alopecia, scaling.
- Tinea corporis: torso. “Ringworm” ( Erythematous scaling rings with central clear). Can be acquired from contact with an infected cat or dog.
- Tinea Cruris: inguinal area.
- Tinea pedis: three varieties: 1) interdigital 2) moccasin distribution
3) vesicular type - Tinea unguium: onuchomycosis (nails)
Cutaneous mycoses
Tinea (pityriasis) versicolor
Malassezia furfur
Pathogenesis: degradation of lipids produces acids that damage melanocytes and cause hypopigmented and/or pink patches.
The lesions are in the chest and back
Most common in summer (moist, warm climates)
Dx: microscopy with KOH SHOWS “ spaghetti and meatballs”
Coppery -orange fluorescence under wood lamp
Tx: selenium sulfide, topical and/or oral antifungal medications
Subcutaneous mycoses
Sporothrix schenckii
- Sporotrichosis (rose gardener disease) subcutaneous / lymphocutaneous mycetomas.
- Sporotrichosis pulmonar: alcoholic rose garden sleeper disease (homeless, urban alcoholics)
Dimorphic fungus : *environmental form: on plant material as hyphae with rosettes and sleeves of conidia. * Tissue form: cigar-shaped yeast.
Transmission: traumatic implantation (rose)
Dx: cigar shaped yeast in pus.
Tx: itraconazole or potassium iodide
Opportunistic Fungi
AIDS Patients
- Aspergillus fumigatus
- Candida albicans
- Cryptococcus neoformans ( most common cause of meningitis in inmunocompromised )
- Mucor and Rhizopus spp.
- Pneumocystis jirovecii
Candida albicans
- Yeast endogenous to our mucous membrane normal flora.
- Inmunocompromised patient, overuse of antibiotics , IV drug abusers.
- Discharge will be like cut cheese
- Diseases: *Oral and esophageal thrush in inmunocompromised
* Vulvovaginitis
* Diaper Rash
* Endocarditis
* Chronic mucocutaneous candidiasis - Dx: KOH , Septicemia needs culture
- tx: topical imidazoles or oral ; nystatin
Disseminated: amphotericin B or fluconazole
Aspergillosis
- Causal agent: Aspergillus fumigatus
- monomorphic filamentous fungus: acute angles, frequent septate hyphae with 45 grades angles
- risk : patient with asthma, cystic fibrosis, patient with cavity lung, patient with burns
- Allergic bronchopulmonary aspergillosis and invasive aspergillosis (severe neutropenia)
Cryptococcus neoformans
Heavily encapsulated yeast. Not dimorphic
Environment source: soil enriched with pigeon droppings .
Acquired through inhalation with hematogenous dissemination to meninges.
Dx: culture in sabouraud agar , India ink
Diseases: - cryptococcosis
- cryptococcal meningitis
- encephalitis (lesions in brain “soap bubble”)
Risk: inmunocompromised patients
Tx: Amb+ flucytosine per 10 weeks, then fluconazole
Mucor and Rhizopus spp.
Mucormycosis= rhinocerebral infection= zygomycosis
Paranasal swelling, necrotic tissue, hemorrhagic exudates from nose and eyes (black color) and mental lethargy . Headache, facial pain, may have cranial nerve involvement
Patients risk: ketoacidotic diabetic patients and leukemic patients
Pathogenesis: fungi proliferate in the blood vessel walls, penetrate cribiforme plate and enter brain.
Pneumocystis jirovecii
Fungus, obligate extracellular parasite.
Cause Pneumocystis Pneumonia in AIDS: diffuse interstitial pneumonia
Symptoms: fever, cough, shortness of breath, sputum nonproductive except in smokers
X-ray: patchy infiltrative (ground glass appearance)
Dx: x Ray, clinic, silver staining cysts in bronchial alveolar lovage fluids or biopsy.
Tx: TMP-SmX for mild, dapsone for moderate to severe.
