3. Fungi and Parasites Flashcards
Fungal spores
Most fungal spores are asexual. Both coccidioidomycosis and histoplasmosis are transmitted by inhalation of asexual spores. Conidia = asexual fungal spores (e.g., blastoconidia, athroconidia)
Histoplasmosis. Location, Presentation, Findings
Dimorphic fungi that can cause systemic mycosis, endemic to Mississippi and Ohio river valleys. Causes pneumonia. In bird or bat droppings. Intracellular (tiny yeast inside macrophages [below]):
Blastomycosis. Location, presentation, findings
Dimorphic fungi that can cause systemic mycosis, endemic to states east of Mississippi River and Central America Causes inflammatory lung dz and can disseminate to skin and bone. Forms granulomatous nodules. Big, Broad-Based Budding: Culture on Sabouraud’s agar.
Coccidioidomycosis
Dimorphic fungi that can cause systemic mycosis, endemic to Southwestern USA, California. case rate increase after earthquakes (spores in dust thrown up in air and become spherules in lungs). Causes pneumonia and meninngitis; can disseminate to bone and skin. Found in San Juoquin Vally or desert (desert bumps) vally fever; spherule filled with endospores (much larger than RBC)
Paracoccidioidomycosis
Budding yeast with “captain’s wheel” formation much larger than RBC. Latin America.
What are the Dimorphic fungi. Treatment for local and systemic infections.
(Histoplasmosis, Blastomycosis, Coccidioidomycosis, and Paracoccidioidomycosis) Mold in soil (@ lower temps) and yeast in tissue (@higher/body temp: 37C), except coccidioidomycosis, which is a spherule in tissue. Cold = Mold, Heat = Yeast All can cause pneumonia and can disseminate. Tx: fluconazole or ketoconazole for local infxn, amphotericin B for systemic infxn. Systemic mycoses can mimic TB (granuloma formation)
Tinea versicolor. Agent, Etiology/Presentation, Treatment, Finding
Caused by Malassezia furfur. Degradation of lipids produce acids taht damage melanocytes and cause hypopigmented and hyperpigemented patches. Occurs in hot, humid weather. Tx: topical miconazole, selenium sulfide (Selsun). Spaghetti and meatballs appearance on KOH prep.
Tinea pedis, cruris, corporis, capitis
Pruritic lesions w/ central celaring resembling a ring, caused by dermatophytes (Microsporum, Trichophyton, and Epidermophyton). See mold hyphae on KOH prep, not dimorphic. Pets are a reservoir for Microsporum and can be treated w/ topical azoles.
Candida albicans ( alba = white)
Systemic or superficial fungal infxn. Yeast w/ pseudohyphae in culture at 20C; germ tube formation at 37C (diagnostic).
Candida albicans Causes what?
Causes: Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS) Vulvovaginitis (high pH, diabetes, use of ABX) Diaper rash Endocarditis in IV drug users Disseminated candidiasis (to any organ) Chronic mucocutaneous candidiasis
Candida albicans Tx?
Nystatin for superficial infxn Amphotericin B for serious systemic infxn
Aspergillus fumigatus Causes what?
Causes: Allergic bronchopulmonary aspergillosis Lung cavity aspergilloma (fungus ball) Invasive aspergillosis, especially in immunocompromised indvls and those w/ chronic granulomatous dz
Aspergillus fumigatus
Mold w/ septate hyphae that branch at a V-shaped (45 degree) angle Not dimorphic.
Cryptococcus neoformans Causes what?
Causes: Crytococcal meningitis Cytococcosis
Cryptococcus neoformans
Heavily encapsulated yeast . Not dimorphic. Found in soil, pigeon droppings.
Cryptococcus neoformans Culture? Identification?
Culture w/ Sabouraud’s agar. Stains w/ India ink. Latex agglutination test detects pollysaccharide capsular Ag. Soap bubble lesions in brain.
Mucor and Rhizopus species
Cause mucormycosis. Mold w/ irregular nonseptate hyphae branching at wide angles (> 90 degrees).
Mucormycosis epidemiology/pathogenesis
(caused by Muro and Rhizopus spp.) Dz most likely in ketoacidotic diabetic and leukemic pts. Fungi also proliferate in the walls of blood vessels and cause infarction and necrosis of distal tissue. Rhinocerebral, frontal lobe abscesses.
Pneumocystis jiroveci (formerly carinii) Causes what? Mode of transmission? In whom?
Causes diffuse interstitial pneumonia. Most infxns asymptomatic. Inhaled. Immunosuppression predisposes to dz.
Pneumocystis jiroveci (formerly carinii) (organism)
Yeast (originally classified as protozoan). Identified by methenamine silver stain of lung tissue.
Pneumocystis jiroveci (formerly carinii) Dx?
Diffuse, bilateral CXR appearance. Dx by lung biopsy or lavage: identified by methenamine silver stain of lung tissue.
Pneumocystis jiroveci (formerly carinii) Tx?
TMP-SMX, pentamidine, dapsone. Start prophylaxis when CD4 drops < 200 cells/mL in HIV pts.
Sporothrix schenkii Causes what?
Sporotrichosis. When traumatically introduced into the skin, typically by a thorn (rose gardener’s dz), causes local pustule or ulcer w/ nodules along draining lymphatics (ascending lymphangitis). Little systemic illness.
Sporothrix schenkii Organism?
Dimorphic fungus that lives on vegetation. Cigar-shaped budding yeast visible in pus.
