Chapter 20: Fungi
Terms
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- What are pseudohyphae?
- Long chains of unicellular yeast cells
- Molds are aka?
- Mycelia
- What are dimorphic fungi? Examples?
- Growing as spores in the environment, often as yeast in the body. Histoplasma, blastomyces, and coccidioides
- Which fungus has a polysaccharide capsule?
- Cryptococcus neoformans
- What's the classic way of getting sporotrichosis? Manifestations?
- Gardener getting a rose thorn prick, with the gradual formation of a subQ nodule. This necroses and ulcerates, spreading along lymphatic tracts up the arm
- How is sporotrichosis treated?
- Oral potassium iodide or amphotericin B.
- What are the three fungi that cause systemic disease in humans? They are endemic to where?
- Histoplasma, blastomyces, and coccidioides. Histo and blasto are Mississippi river fungi, wheras coccidioides is found in the southwest.
- The disease mechanism of systemic fungal infections is similar to...? Describe in general...?
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Similar disease mechanism to TB.
1. Inhalation of spores
2. Local lung infection followed by bloodstream dissemination.
3. In most people, the fungi are then destroyed by cell-mediated immunity. - What are the clinical presentations of the systemic fungal infections?
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1. Asymptomatic
2. Pneumonia - chest Xray infiltrates, granulomas with calcifications can follow resolution of the pneumonia.
3. Disseminated disease - meningitis, bone lytic granulomas, skin granulomas/ulcers, and other organ lesions - What's the best way of diagnosing systemic fungal infections?
- Tissue biopsy
- Treatment for chronic or disseminated fungal disease is usually...?
- Itraconazole or amphotericin B
- What is the major manifestation of cryptococcus infection? Seen in which population?
- Meningoencephalitis (3/4 of cases occur in immunocompromised persons such as AIDS patients)
- Why is cryptococcal meningitis fatal without treatment?
- Cerebral edema progresses to eventual brainstem compression.
- What is the key to cryptococcus diagnosis?
- Lumbar puncture and analyzing the CSF. Also make sure to measure opening pressure.
- What is the usual treatment of an AIDS patient with cryptococus infection?
- Amphotericin B and flucytosine
- Describe where Candida can be seen in normal immunocompetent hosts?
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1. Oral thrush
2. Vaginitis
3. Diaper rash - What are the risk factors for developing vaginitis?
- Women taking antibiotics, oral contraceptives, or during menses and pregnancy
- What are the more serious manifestations of Candida in immunosuppressed patients? What should be examined in these patients?
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1. Esophagitis
2. Disseminated - Can invade virtually every organ
Examine retina for cotton spots, check blood cultures. - What is an aspergilloma?
- An aspergillus fungal ball in the lung cavitations from TB or malignancies.
- What mycotoxin is produced by Aspergillus? What does it do?
- Aflatoxin - causes liver damage and liver cancer.
- What disease does Actinomyces cause? What is an important microscopic feature of Actinomyces?
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Eroding abscesses following trauma to the mucous membranes of the mouth or GI tract.
Sulfur granules. - Describe Nocardia microscopically? Frequently misdiagnosed as?
- Partially acid-fast beaded branching thin filaments. Frequently misdiagnosed as TB.
- Describe treatment for Actinomyces and Nocardia?
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Treatment is a SNAP!
Sulfa for Nocardia, Actinomyces give Penicillin. - Describe the adverse effects (and ways to mitigate them) of Amphotericin B?
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1. Renal toxicity (administer with normal saline)
2. Acute febrile reaction (give aspirin)
3. Anemia
4. Phlebitis of the vein at the IV site