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Fungi
overview
- Yeasts: round fungi that reproduce by budding with smooth colonies on agar
- -Candida
- -Cryptococcus (cryptococcus neoformans - endemic)
- Mold: filamentous fungi consisting of tubular structures called hyphae that grows by branching or longitudinal extension with fuzzy colonies on agar
- -Aspergillus
- -Mucorales
- Dimorphic: grwo in the host as yeast; grow outside the host as molds (aka "endemic" fungi; regionally endemic)
- -Histoplasma capsulatum
- -Coccidioides immitis
- -Blastomyces dermatitidis
- -Paracoccidioides brasiliensis
- (Cryptococcus neoformans is an endemic yeast)
Opportunistic fungi: generally only cause significant disease in those who are immunocompromised
- Dx: identification of organism
- -Yeasts: biochemical tests
- -Molds: appearance
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Histoplasmosis
Complications, Dx, treatment
- Complications:
- -Pericarditis (6%)
- -mass-like lesion
- -mediastinal fibrosis
- -chronic cavitary disease
- -disseminated disease (especially immunocompromised)
- -Liver and splenic calcifications common in healed acute histoplasmosis
- Dx:
- -Culture on brain heart infusion agar (positive in 10% of acute cases, 60% with cavitary disease, 90% in AIDS pts with progressive disseminated disease)
- -Antigen detection in urine (positive in 20% of acute cases, 40% with cavitary disease, 90% with progressive disseminated)
- -Serology (can follow titers to monitor progression; if it becomes disseminated)
- Tx:
- -Many recover spontaneously and don't need treatment
- -Itraconazole if symptomatic, hypoxemic
- -Liposomal Amphotericin B if severely ill
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- Histoplasma capsulatum
- Wright-Giemsa stain
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- H. capsulatum
- Silver Stain
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Valley Fever
Coccidioides immitis
- -San Joaquin Valley (Imperial Valley)
- -Outbreak where soil disturbed
- Coccidioides immitis:
- -Infectious form: arthroconidia (inhaled, land in terminal bronchioles)
- -Change into spherules and cause local inflammation
- -Acute infection involves neutrophils and eosinophils
- -later: granulomatous inflammation
- -Dissemination occurs --> endospores within macrophages
- Immune response:
- -Control requires T lymphocytes
- -those w/disseminated infection don't make interferon gamma in response to cocci antigens
- -Disseminated infection is more common in African Americans, Latinos, Filipinos
- Illness:
- -endemic areas, may be responsible for up to 1/3 CAP
- -incubation 7-21 days
- -Sx: cough, chest pain, SOB, fever, fatigue, weight loss
- Complications:
- -Erythema multiforme
- -Erythema nodosum
- -Migratory arthralgias
- -Hilar adenopathy may persist
- -Nodules may develop
- -Initial lesions may cavitate
- CxR:
- Acute
- Chronic
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Disseminated Cocci
- CxR often normal
- Skin disease
- meningitis
- Joint and bone involvement
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Coccidioides
diagnosis and treatment
- Dx:
- -Demonstration of fungus in tissue
- -growth from culture
- -Serology: Precipitin, Complement fixation, immunodiffusion, ELISA
- -Skin testing used to be available (not done now)
- Tx:
- -Depends on extent of disease
- -Amphotericin
- -Fluconazole
- -Dissemination generally requires lifelong suppression
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Blasto
Pathogenesis and pathology
- -Lung is the portal of entry
- -most cutaneous disease is from hematogenous spread
- Path: similar to cocci: polys f/b noncaseating granulomas
- -cutaneous disease has pseudoepitheliomatous hyperplasia and microabscesses - may mimic squamous cell carcinoma
- Immunity:
- -Polys and macrophages can control conidia, but not yeast
- -T cells needed to control infection once yeast forms present
- Clinical presentation:
- -Many/most infections asymptomatic
- -Pulmonary infection may be acute or chronic
- -Skin, bone, GU tract are the most common extrapulmonary sites
- -Incubation period: 30-45 days
- -Sx: cough, myalgias, arthralgia, chills, fever
- -Pleuritic pain may be prominent but transient
- Imaging:
- -Lobar or segmental consolidation of CxR
- -Pleural fluid uncommon
- -Hilar adenopathy uncommon
- Chronic: present almost like lung cancer
- -weight loss
- -cough
- -anorexia
- -hemoptysis
- -pleuritic chest pain
- Dx:
- -cytology, wet mount
- -culture positive in 75% (92% in bronchoscopy)
- -PAS or GMS stains of tissue
- -Serology not very sensitive nor specific
- -Antigen detection in urine +93%
- Tx:
- -Acute disease: treat (not the wait and watch)
- -Azoles for mild-moderate
- -Amphtericin B f/b itraconazole for severe infection
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