fungi

Question 1

what are the four major phyli of fungi?

Answer 1

chytridiomycota, 
zygomycota, 
ascomycotam 
basidiomycota, 
deuteromycetes

Question 2

charactersitcs of fungi? 7

Answer 2

cell wall made of chitin and glucan,
 and a eukaryotic avascular.
heterotrophic
glycogen storing
ergosterol in membrane
tubule protein
dimorphic

Question 3

antifungals target what aspects of fungi?

Answer 3

membrane sterols

and biosynthetic and metabolic fnxs that are different bw fungi and humans

Question 4

how does amphotericin work?

Answer 4

makes fungi membranes leaky by interaction with sterols in membrane. Gives severe side effects bc targets ergosterol and cholesterol.

Question 5

how do azoles work?

Answer 5

rings that inhibit cyochrome P450-dependent enzymes, involved in synthesis of membrane sterols.

Question 6

how do echinocandins work?

Answer 6

inhibition of UDP which is associated with glucan synthesis in various fungi- cell wall

Question 7

Which type of immunity does body impart to fight fungal infection?

Answer 7

Th1 for protective immunity after an innate initial PMN-cytokine response.

Question 8

What mycoses cause infections of skin and its appendages?

Answer 8

cutaneous: microsporum, trichophyton, and epidermophyton

Question 9

What kind of infection does sporotrix schenkii cause?

Answer 9

subQ ulcerated lesions with nodules.

Question 10

What is the most virulent fungal pathogen? How is it encountered?

Answer 10

coccidiomycosis. Inhalation of spore from SW US soil, limited to pulmonary system but is spreadable. Immunosuppressed pt.

Question 11

What factors does coccidiomycosis use to evade defense mechanisms?

Answer 11

hydrophobic outer wall and an alkaline halo of urease.

Question 12

What is the growth patter of histoplasma capsulatum?

Answer 12

macrophage centered intracellular growth causing a granulomatous reaction and flu-like symptoms.

Question 13

How is histoplasmosis encountered?

Answer 13

Bat dropping infested soil yeast from Ohio-Mississippi river valley

Question 14

What tests can we perform to diagnosis histoplasmosis infection?

Answer 14

culture histology
serological testing- Ag and Ab
urine test- Ag detection in HIV pt

Question 15

what is the treatment for histoplasmosis?

Answer 15

amphotericin (disseminated ds) and ketoconasole (limited ds)

Question 16

What kind of illness does Blastomycosis typically present as?

Answer 16

granulomatous infection of skin and lungs, but spreadable. In men and children.

Question 17

How does one encounter blastomycosis?

Answer 17

Inhalation of spores from the dimorphic fungi in southern US soil, limited to pulmonary and skin systems.

Question 18

How is blastomycosis responded to?

Answer 18

macrophages try, then PMNs try but large size of yeast make it hard to kill, then Th1 as the major defense. Can evade defenses by shedding surface ag.

Question 19

Treatment of blastomycosis includes?

Answer 19

amphotericin B and itraconazole/fluconazole

Question 20

Which fungi are considered opportunisitc mycoses?

Answer 20

aspergillosis
candidiasis
cryptococcus
pneumocystitis carinii
zygomycosis

Question 21

What is the method of enounter and defense against cryptococcus?

Answer 21

pigeon poop inhalation to lungs, that spreads via blood to cause meningitis. CMI is primary defense.

Largely seen in lymphoma and AIDS pt due to their immunosuppresion

Question 22

How does cryptococcus evade host defenses?

Answer 22

Evades host via capsule that is resistant to phagocytosis and melanin that is protective against ox damage.

Question 23

How do we diagnose cryptococcus? Treatment?

Answer 23

lumbar puncture and CSF histology. Culture of organisms from blood/CSF looking for ag.

Tx: amphotericin B and fluconazole

Question 24

What is the most commonly found fungi in environment? How is it encountered? Most common underlying disease?

Answer 24

Aspergillosis: inhaled from soil/water/food and disseminates from lungs to around.

Those with neutropenia and corticosteriod users.(mainly hematological patho as underlying ds)

Question 25

Which fungal infection is caused by a member of indigenous microflora of humans?

Answer 25

candidiasis is found in GI, URT and vagina. Antibiotic usage leads to invasion, as well as catheter usage. Presents with yeast, hyphae and pseudohyphae in vivo.

Question 26

How does host defend against cadidiasis? Who is at risk?

Answer 26

Hyphae are too big for PMNs so their fnx is to damage hyphae. lymphocytes inhibit its growth. Invasion is inhibited by phagocytosis, complement, AB and TCMI.

Post-op pt, cancer pt, ppl on Abiotics, burns, drug abusers and GI damaged ppl are at risk.

Question 27

treatment of chronic mucocutaneous candiadisis?

Answer 27

oral azole antibiotics

Question 28

What kind of infections does zygomycosis cause?

Answer 28

diabetics- facial/eye pain and sinus infection

pulmonary, GI, cutaneous

Question 29

What are the key clinical features of candida infection? what do we do for treatment?

Answer 29

persistent fever post ‘trauma’ and antibiotics. Urine cultures +, blood cultures - (early!) High mortality when waiting for blood cultures to become pos.

Remove immunosuppression and give antifungals ASAP. Unless disseminated, can give either amphotericin or caspofungin. Disseminated: amphotericin always.

Question 30

What is the treatment for aspergillosis? At what stage is most reactive to treatment?

Answer 30

polyenes (DNA synth)
azoles- Voriconazole is recommended
echinocandins

halo sign +

Question 31

Which antifungal is zygomycetes most resistant to?

Answer 31

voriconazole. Its a breakthrough infection for pt under that antifungal for other reasons.