Microbiology: Fungi

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jknell
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195785
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Microbiology: Fungi
Updated:
2013-04-05 12:14:49
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Fungi
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  1. Systemic mycoses
    • All can cause pneumonia and can disseminate:
    • -Histoplasmosis
    • -Blastomycosis
    • -Coccidioidomycosis
    • -Paracoccidioidomycosis

    • All are dimorphic fungi:
    • -Cold (20°C) = mold
    • -Heat (37°C) = yeast

    Exception: coccidioidomycosis is a spherule (not yeast) in tissue.

    • Tx: 
    • -fluconazole or ketoconazole for local infection
    • -amphotericin B for  systemic infection

    Systemic mycosis can mimic TB (granuloma formation), except (unlike TB) have no person-person transmission
  2. Histoplasmosis
    Endemic location: Mississippi and Ohio river valley

    Disease: pneumonia

    Pathology: Macrophage filled with Histoplasma (smaller than RBC)

    Histo Hides (within macrophages). Bird or bat droppings
  3. Blastomycosis

    Endemic location: east of Mississippi River and Central America

    Disease: inflammatory lung disease that can disseminate to skin and bone. Forms granulomatous nodules

    Pathology: Broad-base budding (same size as RBC)

    Blasto Buds (Broadly)
  4. Coccidioidomycosis

    Endemic location: Southwestern US, California

    Disease: pneumonia and meningitis; can disseminate to bone and skin

    Spores in dirt; increased rate after earthquakes

    Pathology: Spherule filled with endospores (much larger than RBC)

    Coccidio Crowds. San Joaquin Valley (or Imperial Valley) or desert "valley fever"
  5. Paracoccidioidomycosis
    • Endemic location:Latin America
    • -Rare, but most severe

    Budding yeast with "captain's wheel" formation (much larger than RBC)

    Captain wheel appearance. Paracoccidio Parasails with the captain's wheel all the way to Latin America
  6. Fungi
    endemic locations
  7. Cutaneous mycoses
    • 1. Tinea versicolor
    • - Caused by Malassezia furfur. Degradation of lipids produces acids that damage melanocytes and cause hypopigmented and/or hyperpigmented patches
    • -Occurs in hot, humid weather

    Tx: Topical miconazole, selenium sulfide (Selsun)

    Spaghetti and meatball appearance on KOH prep



    • 2. Other tineae
    • -tinea pedis (foot), tinea cruris (groin), tinea corporis (ringworm, on body), tinea capitis (head, scalp)
    • -Pruritic lesions with central clearing resembling a ring, caused by dermatophytes (Microsporum, Trichophyton, and Epidermophyton)

    See mold hyphae in KOH prep, not dimorphic
  8. Opportunistic fungal infections
    • Candida albicans
    • Aspergillus fumigatus
    • Cryptococcus neoformans
    • Mucor and Rhizopus spp.
    • Pneumocystis jiroveci
    • Sporothrix schenckii
  9. Candida albicans
    Systemic or superficial fungal infection

    • -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

    Tx: topical azole for vaginal; fluconazole or caspofungin for oral/esophageal; amphotericin B, fluconazole, or caspofungin for systemic
  10. Candida albicans

    (alba = white)
  11. Aspergillus fumigatus
    Invasive aspergillosis - especially in immunocompromised and those with chronic granulomatous disease

    • 1. Allergic bronchopulmonary aspergillosis: with asthma or CF
    • 2. Aspergillomas in lung cavities especially after TB infection
    • 3. Some species of Aspergillus produce aflatoxins, which are associated with hepatocellular carcinoma
    • 4. Invasive and/or disseminated disease in immunocompromised patients, especially in lungs. 

    *Think "A" for Acute Angles in Aspergillus



    NOT dimorphic
  12. Cryptococcus neoformans
    Cryptococcal meningitis, cryptococcosis

    -Heavily encapsulated yeast. Not dimorphic

    • -Found in soil, pigeon droppings
    • -Acquired through inhalation with hematogenous dissemination

    -Culture on Sabouraud's agar. Stains with India ink. Latex agglutination test detects polysaccharide capsular antigen and is more specific.



    "Soap bubble" lesions in brain
  13. Mucor
    and Rhizopus spp.
    Mucormycosis. Disease mostly in ketoacidotic diabetic and leukemic patients

    Fungi proliferate in blood vessel walls when there is excess ketone and glucose, penetrate cribiform plate, and enter brain.

    Rhinocerebral, frontal lobe abscesses

    Headache, facial pain, black necrotic eschar on face; may have cranial nerve involvement

  14. Pneumocystis jiroveci
    Causes diffuse interstitial pneumonia

    • Yeast
    • Inhaled

    • -most infections are asymptomatic
    • -Immunosuppression predisposes to disease
    • -Diffuse, bilateral CXR appearance

    Dx: lung biopsy or lavage

    • Disk-shaped yeast forms on methenamine silver stain of lung tissue

    • Tx: TMP-SMX, pentamidine, dapsone.
    • -Start prophylaxis when CD4 drops <200 cells/mL in HIV patients
  15. Sporothrix schenckii
    • Sporotrichosis
    • Dimorphic, cigar-shaped budding yeast that lives on vegetation

    • -When 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). 
    • -Little systemic illness

    Tx: itraconazole or potassium iodide. ("Plant a rose in the pot")

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