Microbiology - Mycology Flashcards
1
Q
Systemic mycoses
- Examples
- Can cause…
- Caused by/
- Treatment
- Mimic…
A
- Examples
- Histoplasmosis, Blastomycosis, Coccidioidomycosis, Paracoccidioidomycosis
- Can cause pneumonia and can disseminate.
- Caused by dimorphic fungi
- Cold (20°C) = mold; heat (37°C) = yeast.
- The only exception is coccidioidomycosis, which is a spherule (not yeast) in tissue.
- Treatment:
- Fluconazole or itraconazole for local infection;
- Amphotericin B for systemic infection.
- Systemic mycoses can mimic TB (granuloma formation), except, unlike TB, have no person-person transmission.
2
Q
Histoplasmosis
- Location
- Causes…
- Features
- Transmission
A
- Location
- Mississippi and Ohio River valleys.
- Causes…
- Causes pneumonia.
- Features
- Macrophage filled with Histoplasma (smaller than RBC) [A].
- Histo hides (within macrophages).
- Transmission
- Bird or bat droppings.
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3
Q
Blastomycosis
- Location
- Causes…
- Features
A
- Location
- States east of Mississippi River and Central America.
- Causes…
- Causes inflammatory lung disease and can disseminate to skin and bone.
- Features
- Forms granulomatous nodules.
- Broad-base budding (same size as RBC) [B].
- Blasto buds broadly.
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4
Q
Coccidioidomycosis
- Location
- Causes…
- Incidence
- Features
A
- Location
- Southwestern United States, California.
- “(San Joaquin) Valley fever”
- Causes…
- Causes pneumonia and meningitis
- Can disseminate to bone and skin.
- Incidence
- Case rate increases after earthquakes (spores in dust are thrown up in the air and become spherules in lungs).
- Features
- Spherule (much larger than RBC) filled with endospores [C].
- Coccidio crowds.
- “Desert bumps” = erythema nodosum
- “Desert rheumatism” = arthralgias
- Spherule (much larger than RBC) filled with endospores [C].
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5
Q
Paracoccidioidomycosis
- Location
- Features
A
- Location
- Latin America.
- Features
- Budding yeast with “captain’s wheel” formation (much larger than RBC) [D].
- Paracoccidio parasails with the captain’s wheel all the way to Latin America.
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6
Q
Cutaneous mycoses
- Tinea versicolor
- Caused by…
- Features
- Treatment
- Other tineae
- Includes…
- Features
A
- Tinea versicolor
- Caused by…
- Malassezia furfur.
- Degradation of lipids produces acids that damage melanocytes and cause hypopigmented and/or hyperpigmented patches.
- Features
- Occurs in hot, humid weather.
- “Spaghetti and meatball” appearance [A].
- Treatment
- Topical miconazole, selenium sulfide (Selsun).
- Caused by…
- Other tineae
- Includes…
- Tinea pedis (foot), tinea cruris (groin), tinea corporis (ringworm, on body), tinea capitis (head, scalp), tinea unguium (onychomycosis, on fingernails).
- Features
- Pruritic lesions with central clearing resembling a ring, caused by dermatophytes (Microsporum, Trichophyton, and Epidermophyton).
- See mold hyphae in KOH prep, not dimorphic.
- Includes…
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7
Q
Examples of opportunistic fungal infections
A
- Candida albicans
- Aspergillus fumigatus
- Cryptococcus neoformans
- Mucor and Rhizopus spp.
- Pneumocystis jirovecii
- Sporothrix schenckii
8
Q
Candida albicans
- Features
- Causes…
- Treatment
A
- Features
- alba = white.
- Systemic or superficial fungal infection.
- Causes…
- Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS), vulvovaginitis (diabetes, use of antibiotics), diaper rash, endocarditis in IV drug users, disseminated candidiasis (to any organ), chronic mucocutaneous candidiasis.
- Treatment
- Topical azole for vaginal
- Fluconazole or caspofungin for oral/esophageal
- Ffluconazole, amphotericin B, or caspofungin for systemic.
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9
Q
Aspergillus fumigatus
- Features
- Causes…
A
- Features
- Invasive aspergillosis, especially in immunocompromised and those with chronic granulomatous disease.
- Not dimorphic.
- Causes…
- Allergic bronchopulmonary aspergillosis (ABPA)
- Associated with asthma and cystic fibrosis
- May cause bronchiectasis and eosinophilia.
- Aspergillomas in lung cavities, especially after TB infection.
- Some species of Aspergillus produce aflatoxins, which are associated with hepatocellular carcinoma.
- Think “A” for Acute Angles in Aspergillus.
- Allergic bronchopulmonary aspergillosis (ABPA)
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10
Q
Cryptococcus neoformans
- Causes…
- Features
- Transmission
- Diagnosis
*
A
- Causes…
- Cryptococcal meningitis, cryptococcosis.
- Features
- Heavily encapsulated yeast.
- Not dimorphic.
- “Soap bubble” lesions in brain.
- Transmission
- Found in soil, pigeon droppings.
- Acquired through inhalation with hematogenous dissemination to meninges.
- Diagnosis
- Culture on Sabouraud agar.
- Stains with India ink and mucicarmine.
- Latex agglutination test detects polysaccharide capsular antigen and is more specific.
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11
Q
Mucor and Rhizopus spp.
- Causes…
- Features
- Treatment
A
- Causes…
- Mucormycosis.
- Disease mostly in ketoacidotic diabetic and leukemic patients.
- Rhinocerebral, frontal lobe abscesses.
- Headache, facial pain, black necrotic eschar on face
- May have cranial nerve involvement.
- Features
- Fungi proliferate in blood vessel walls when there is excess ketone and glucose, penetrate cribriform plate, and enter brain.
- Treatment
- Amphotericin B.
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12
Q
Pneumocystis jirovecii
- Causes…
- Features
- Transmission
- Diagnosis
- Treatment/prophylaxis
A
- Causes…
- Pneumocystis pneumonia (PCP), a diffuse interstitial pneumonia.
- Immunosuppression (e.g., AIDS) predisposes to disease.
- Features
- Yeast (originally classified as protozoan).
- Most infections are asymptomatic.
- Transmission
- Inhaled.
- Diagnosis
- Diffuse, bilateral CXR appearance.
- Diagnosed by lung biopsy or lavage.
- Disc-shaped yeast forms on methenamine silver stain of lung tissue [A].
- Treatment/prophylaxis
- TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone (prophylaxis only).
- Start prophylaxis when CD4 count drops < 200 cells/mm3 in HIV patients.
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13
Q
Sporothrix schenckii
- Causes…
- Features
- Transmission
- Treatment
A
- Causes…
- Sporotrichosis.
- Little systemic illness.
- Features
- Dimorphic, cigar-shaped budding yeast that lives on vegetation [A].
- Transmission
- When spores are traumatically introduced into the skin, typically by a thorn (“rose gardener’s” disease), causes local pustule or ulcer with nodules along draining lymphatics (ascending lymphangitis).
- Treatment
- Itraconazole or potassium iodide.
- “Plant a rose in the pot.”
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