111814 fungi

Question 1

common features of histo, blasto, cocci regarding their forms

Answer 1

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

Question 2

infection by histo, blasto, cocci occurs commonly via what route

Answer 2

respiratory

Question 3

definitive diagnosis for histo, blasto, cocci requires

Answer 3

microscopic exam of clinical specimen supplemented as needed with lab cultivation on media and serology

Question 4

geographic distribution of histo, blasto, cocci

Answer 4

blasto-eastern part of US, including Wisconsin
histo-Illinois, Mississippi, etc
cocci-southwestern US

Question 5

favorable environment of Histo in the wild

Answer 5

soil, particularly that containing bird feces

Question 6

morphology of histo

Answer 6

in environment: hyphae, with microconidia and macroconidia

in host: oval budding yeast with NARROW BUD NECK. found inside mononuclear phagocytes and extracellularly

Question 7

main infectious form of histo

Answer 7

likely microconidia b/c of small size and ability to become airborne

Question 8

result of infec with histo in immunocompetent

Answer 8

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

Question 9

clinical syndromes for histo

Answer 9

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

Question 10

virulence factors for histo

Answer 10

microconidia have receptors for CD2/CD18 integrins on surface of macrophages to facilitate phagocytosis

Question 11

antifungal therapy for histo

Answer 11

not all clinical manifestations require drug treatment

anti fungal drugs are considered adjunt to host’s immune system

Question 12

skin test reactivity to histo indicates

Answer 12

in endemic areas, doesn’t necessarily indicate “active” disease because most inhabitants have been exposed

Question 13

how to detect histo organisms in specimens?

Answer 13

PAS and GMS stain

Question 14

blasto’s favorable environment in the wild

Answer 14

rich moist soil

Question 15

geographic distribution of blasto

Answer 15

near MIssissippi River, Ohio River

Question 16

organism morphology of blasto

Answer 16

environment: hyphae producing microconidia
host: large budding yeast with BROAD bud neck

Question 17

incubation time for blasto

Answer 17

4-6 weeks after exposure

Question 18

clinical symptoms for blasto

Answer 18

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

Question 19

compare the surface molecules on blasto vs histo

Answer 19

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

Question 20

challenge to the clinician with blasto

Answer 20

differential diagnosis from other pneumonias, TB, lung cancer

differentiating primary from metastatic cutaneous lesions

Question 21

coccidioides’ favorable environment in wild

Answer 21

soil rich in organic material

hot arid climates

Question 22

organism morphology of cocci

Answer 22

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

Question 23

how is infection by cocci acquired

Answer 23

respiratory route

Question 24

when is cocci incidence high

Answer 24

late summer, early fall

Question 25

clinical syndromes of cocci

Answer 25

in asymptomatic-only evidence of infec is hypersensitivity skin test reactivity to cocci

in symptomatic, spectrum ranging from mild flu-like syndrome developing 7-21 days after exposure to an acute severe pneumonia

Question 26

cocci in the context of pregnancy

Answer 26

extremely perilous time for infec with cocci

also, azole antifungals can be teratogenic

Question 27

antifungal therapy for cocci

Answer 27

95% of acute episodes resolve w/o therapy

Question 28

for mild to moderate dis, what do you treat with for the three?

Answer 28

histo-none or itraconazole
blasto-itraconazole b/c it can progress
cocci-none

Question 29

what do you treat w for severe disseminated disease for the three?

Answer 29

histo-amphotericin B and itraconazole
blasto-same
cocci-same

Question 30

in lung, histo forms

Answer 30

granuloma, like TB