Fun Fungi!

Question 1

Fungi cell structure

Answer 1

eukaryotes with 1) cytoplasmic membrane (ergesterol) and 2) chitin cell wall.

ergesterol = drug target. 
chitin = useful in diagnosis

Question 2

2 types of fungi - what are they?

Answer 2

1) yeast 2) fungi/mould

Question 3

talk about yeast

Answer 3

normal flora, internal source, culture in 24-48 hrs, looks like BUDDING CELLS with or without PSEUDOHYPHAE

examples: CANDIDA, CRYPTOCOCCUS NEOFORMANS - meningitis in immunocompromized pts, has a large capsule

Question 4

talk about fungi/mould

Answer 4

not normal flora, external source, 6 wks to culture, characterized by HYPHAE

example: ASPERGILLUS

Question 5

talk about dimorphic fungi

Answer 5

yeast at body temp, mould in environment.

cause mild, self limiting RESPIRATORY INFECTIONS which can be serious in IMMUNOCOPROMISED.

Question 6

examples of dimorphic fungi (3)

Answer 6

1) histoplasma capsulatum (Ont)
2) blastomyces dermatitdis (cottage country mud)
3) coccidoides immitis (Arizona/ arid SW USA)

Question 7

how do we get mould infections?

Answer 7

host antibiotic therapy or immune suppression (neutropenia = aspergillus, down T cells - histoplasma)

also environmental exposure to moulds

Question 8

2 types of fungal infections:

Answer 8

superficial (dermatophyte - moulds(trichophyton, epidermophyton, microsporum. yeasts (candida)).

systemic - aerosol - dimorphic fungi

Question 9

diagnosing a fungal infection

Answer 9

culture - slow.

clinical samples/smears: KOH mount, KOH mount + calcofluor, gram stain, silver stain.

Question 10

types of pathogenic fungi

Answer 10

primary pathogens (environmental reservoir)

opportunistic pathogens (environmental or commensal reservoir) seen in immunocomp

Question 11

antifungal agents: targeting ergesterol

Answer 11

polyenes (amp B and nystatin), azoles (ketoconazole + triazoles), allylamines (terbinafine)

Question 12

antifungal agents: not targeting ergesterol

Answer 12

griseofluvin (oral, treat nail infections, binds keratin, v toxic - liver, photosensitivity, teratogen, drug interactions)

echinocandin (fungicidal, inhibits b 1-3 glucan synthesis, not metabolized by cpu, excreted renal and through bile)

fluorocytosine - inhibits RNA/DNA synthesis, SHORT 2-4 HR half life, v toxic - bone marrow suppression, hepatotoxicity, nephrotoxic

Question 13

antifungal resistance

Answer 13

polyenes: intrinsic resistance only, C lusitanae.
azoles: resistance can be acquired via: increase/decrease in ergesterol synthesis, absprotpion/efflux changes, decreased affinity for drug