111814 fungi Flashcards
common features of histo, blasto, cocci regarding their forms
phenotype switching-dimorphic
in environment, all exist as free living molds
in host, histo and blasto convert to budding yeast. cocci converts to large endosporulating spherule cotaining many endospores
infection by histo, blasto, cocci occurs commonly via what route
respiratory
definitive diagnosis for histo, blasto, cocci requires
microscopic exam of clinical specimen supplemented as needed with lab cultivation on media and serology
geographic distribution of histo, blasto, cocci
blasto-eastern part of US, including Wisconsin
histo-Illinois, Mississippi, etc
cocci-southwestern US
favorable environment of Histo in the wild
soil, particularly that containing bird feces
morphology of histo
in environment: hyphae, with microconidia and macroconidia
in host: oval budding yeast with NARROW BUD NECK. found inside mononuclear phagocytes and extracellularly
main infectious form of histo
likely microconidia b/c of small size and ability to become airborne
result of infec with histo in immunocompetent
most frequently, asymptomatic or non-specific flu-like syndrome (75-90% of the time)
if there’s symptoms, they start 3-17 days after exposure
clinical syndromes for histo
pulmonary-can resemble miliary TB on XR
acute percarditis
disseminated
ocular histoplasmosis syndrome-fibrosing inflam response against yeast
fibrosing mediastinitis-abnormal inflam response leading to fibrosis
virulence factors for histo
microconidia have receptors for CD2/CD18 integrins on surface of macrophages to facilitate phagocytosis
antifungal therapy for histo
not all clinical manifestations require drug treatment
anti fungal drugs are considered adjunt to host’s immune system
skin test reactivity to histo indicates
in endemic areas, doesn’t necessarily indicate “active” disease because most inhabitants have been exposed
how to detect histo organisms in specimens?
PAS and GMS stain
blasto’s favorable environment in the wild
rich moist soil
geographic distribution of blasto
near MIssissippi River, Ohio River
organism morphology of blasto
environment: hyphae producing microconidia
host: large budding yeast with BROAD bud neck
incubation time for blasto
4-6 weeks after exposure
clinical symptoms for blasto
may be benign, self limiting
or
chronic granulomatous
cutaneous disease develops slowly as subcutaneous nodule or papule
skin is most common site of extrapulm blasto
compare the surface molecules on blasto vs histo
on blasto, they bind integrins on host macrophages but this doesn’t necessarily lead to phagocytosis because of the size of the blasto yeast cell
challenge to the clinician with blasto
differential diagnosis from other pneumonias, TB, lung cancer
differentiating primary from metastatic cutaneous lesions
coccidioides’ favorable environment in wild
soil rich in organic material
hot arid climates
organism morphology of cocci
environment: septate multicellular hyphae with alternate cells developing into barrel shaped arthroconidia
host: arthorconidia convert within 72 hrs to large spherules containing NUMEROUS SMALL ENDOSPORES
how is infection by cocci acquired
respiratory route
when is cocci incidence high
late summer, early fall
