Micro Pulmonary fungal infections 1 Flashcards
What are the major themes of systemic mycoses
environmental (spores/fungi in soil) - not person-to-person, inhaled into lungs, thermal dimorphism, range of severity
What is the differential for systemic mycoses? What is the difference between the two?
TB
source for TB is foreign crowds, systemic mycoses is american dirt
Coccidioides form
dimorphic: mold in soil, spherule in tissue (classic to coccidoides)
What are the forms of coccidioides in the soil?
hyphae with alternating arthrospores and empty cells (arthrospores carried in the wind)
Pathogenesis coccidioides
arthrospores are inhaled and change for to spherules in lung (thick, double-refractive wall that is filled iwth endospores), wall ruptures to release endospores and develop into new spherules, spreading by direct extension, while growth leads to granulomatous lesions
What type of immunologic response is there to coccidioides?
CMI delayed hypersensitivity response (infection contained in granulomas in lung)
What happens in a immunosuppressed patient with coccidioides?
disseminated infection by hematogenous spread, primarily seen in bones and meninges
How is coccidioides diagnosed?
PPD with coccidioidin or spherulin (+ if exposed with cleared or contained infection and - if unexposed or DISSEMINATED infection)
Contained coccidioides infection?
asymptomatic, +PPD, influenzealike illness (fever, cough), 50% have lung changes on X-ray, 10% develop erythema nodosum or arthralgias
Erythema nodosum
sign of good strong immune response: “desert bumps” - red, tender nodules on exterior surfaces like lower legs, a delayed cell-mediated hypersensitivity to fungal antigens
Disseminated coccidioides infection?
affects meninges, bone (osteomyelitis), and skin (nodules)
-disseminates MC in AA, Filipino, late-pregnancy
Diagnostic feature of coccidioides
- spherules on microscopic exam!!!
- cultures of sabouraud’s agar (cultures are infectious!)
- serology for exposure, titers (spikes if disseminating)
treatment of coccidioides
- none for mild disease
- persisting lung lesions or disseminated: amphotericin B or itraconazole
- meningitis: fluconazole
endemic areas coccidioides
SW US
histoplasma form
dimorphic: mold in soil, yeast in tissue
what are the two asexual spores formed by histoplasma?
- tuberculate macroconidia (grows in culture) - thick walls and fingerlike projections
- microconidia (infectious form from environment) - smaller, thin, smooth-walled
where is histoplasma endemic? mode of transmission?
ohio and mississippi river valleys - transmitted by soil and bird droppings (starlings and bat guano esp)
histoplasma pathogenesis
spores are inhaled, engulfed by macrophages, survive endocytosis, replicate as yeasts in macrophages and spread through the body
how does histoplasmosis survive endocytosis?
produces bicarbonate and ammonia, raising pH and inactivating hydrolytic enzymes
how do healthy people’s immune response respond to histoplasmosis?
CMI forms granulomas, calcify, and contain infection (may see erythema nodosum)
histoplasmosis in immunocompromised/immunosuppressed
pancytopenia and ulcerated lesions on tongue
histoplasmosis exam
cavitary lung lesions that cause the “jug sound”, granulomas in liver and spleen, tongue lesions in disseminated disease
labs for histoplasmosis
- tissue biopsy or bone marrow aspirate for oval yeast cells within macrophages
- cultures on sabouraud’s agar (25 tuberculate macroconidia, 37 yeast)
treatment for histoplasmosis
if spreading, itraconazole
if disseminated, amphotericin B
if meningitis fluconazole
