Dimorphic Fungi

5 Written Questions

1. 1. Pulmonary Infection
   2. Cough
   3. Fever
   4. Malaise
   5. Weight loss
2. 1. The shift from mold to yeast involves induction of the heat shock response and uncoupling of oxidative phosphorylation
   2. This is followed by shutdown of RNA synthesis
   3. The cells then pass through a metabolically inactive phase
   4. The metabolism in the yeast phase shifts to sulfhydryl compounds
   5. This is reversible and is one of the major virulence factors of these organisms
3. 1. Mycelial forms with spores at 25 C
   2. Yeast forms at 37 C
4. Blastomycosis
   1. Asymptomatic (uncommon)
   2. Pneumonia: lesions rarely calcify (most common)
   3. Disseminated (uncommon): present with weight loss, night sweats, lung involvement, and skin ulcers
   4. Cutaneous: skin ulcers
5. 1. fevers, sweats, weight loss
   2. in disseminated disease, skin & subcutaneous nodules and mucous membrane ulcerations are not unusual (tongue, larynx)

5 Matching Questions

1. Coccidioides immitis Pathogenesis
2. Paracoccidioides brasiliensis Pathogenesis & Clinical disease
3. Histoplasma capsilatum Immunity
4. Paracoccidioides brasiliensis Treatment
5. Blastomyces dermatitidis Immunity

1. a 1. Conidia are inhaled
   2. Once inside host, the conidia change into spherules due to increased temp, lower pH and interactions with phagocytes
   3. The spherule is a "sac" of endospores which are released and lead to new spherules
   4. Proteases released by the spherule are virulence factors
   5. They destroy collagen, elastin and immunoglobulins
2. b 1. The main control of this organism is by cell mediated immunity
   -Mainly the T-cell activation of macrophages
   
   2. Neither B cells or antibody have a significant role
3. c 1. The conidia are inhaled and are usually contained and cleared
   2. Chronic disease with pulmonary and/or lymph node involvement
   3. If a person develops pulmonary infection, they develop cough, fever, malaise, weight loss
   4. Can also affect mucous membranes of the mouth, larynx
4. d 1. Not clear what the predominant host response is
   2. Complement, antibody and cell mediated immunity are all involved
5. e 1. trimethoprim/sulfamethoxazole (TMP sulfa): 1st choice
   2. itraconazole and amphotericin B

5 Multiple Choice Questions

1. 1. Biopsy of affected tissue: lung, skin, etc
   A. silver stain specimen
   B. culture on Sabouraud's agar
   2. Serology
   3. Skin tests (tests for exposure only)
   
   *For skin infections, direct demonstration of the yeast with broad based budding is diagnostic
   1. Blastomyces dermatitidis Diagnosis
   2. Blastomyces dermatitidis Pathogenesis
   3. Blastomyces dermatitidis Immunity
   4. Bastomyces dermatitidis Disease
2. Dimorphic
   1. Mycelial forms with spores at 25 C
   2. Yeast forms at 37 C
   1. Coccidioides immitis Reservoir
   2. Coccidioides immitis Immunity
   3. Coccidioides immitis Morphology
   4. Coccidioides immitis Treatment
3. 1. Central and S. America
   2. Brazil
   1. Paracoccidioides brasiliensis Morphology
   2. Paracoccidioides brasiliensis Diagnosis
   3. Paracoccidioides brasiliensis Reservoir
   4. Paracoccidioides brasiliensis Treatment
4. 1. Mississippi river valley extending north to the great lakes
   2. Resides in soil or rotten wood
   3. Respiratory transmission
   1. Bastomyces dermatitidis Disease
   2. Blastomyces dermatitidis Treatment
   3. Blastomyces dermatitidis Diagnosis
   4. Blastomyces dermatitidis Reservoir
5. 1. Life long immunity does develop
   2. Conidia can be phagocytosed and killed by PMNs
   3. The endospores cannot be handled until macrophages are activated by T-cells (Th1)
   4. Humoral immunity does not play a role
   5. Complement is not effective at opsonizing C. immitis
   1. Coccidiodes immitis Diagnosis
   2. Coccidioides immitis Immunity
   3. Coccidioides immitis Disease
   4. Coccidioides immitis Treatment

5 True/False Questions

1. Paracoccidioides brasiliensis Morphology → 1. trimethoprim/sulfamethoxazole (TMP sulfa): 1st choice
   2. itraconazole and amphotericin B

   True        False

2. Histoplasma capsilatum Pathogenesis → 1. Conidia are inhaled and reach the alveoli
   2. The conidia then convert to yeasts
   3. Survive by capturing iron and calcium from the macrophage
   4. Grow within macrophages
   5. Granulomatous inflammation similar to TB (cell-mediated immunity)

   True        False

3. Coccidioides immitis Disease → Only for disseminated:
   1. Fluconazole (1st choice)
   2. Ampothericin B (2nd choice)

   True        False

4. Coccidioides immitis Reservoir → 1. Desert areas of the southwestern US & northern Mexico
   2. Respiratory transmission

   True        False

5. Histoplasma capsilatum Diagnosis → 1. Conidia are inhaled and reach the alveoli
   2. The conidia then convert to yeasts
   3. Survive by capturing iron and calcium from the macrophage
   4. Grow within macrophages
   5. Granulomatous inflammation similar to TB (cell-mediated immunity)

   True        False