Intro to Fungus

Question 2

what are conidia?

Answer 2

spores of dimorphic fungi that are easily aerosolized and inhaled

Question 3

what subpopulation is most at risk for fungal infection?

Answer 3

immunosuppressed or immunodeficient

Question 4

what are the three major categories of fungal infection?

Answer 4

1. superficial infection of skin/mucous membranes, 2. self-limited mild flu-like illness, 3. invasive and life threatening infections in diabetics/immunosuppressed

Question 5

what is a yeast?

Answer 5

unicellular fungus that reproduces by budding (ex. Candida, cryptococcus)

Question 6

what is a mold?

Answer 6

multicellular fungus with filamenous hyphae that reproduces by sporulation (ex. Aspergillus, zygomycetes, fusirium)

Question 7

how to identify yeast

Answer 7

5-10x larger than bacteria, oval shaped

Question 8

what is a dimorphic fungus, and which form is infectious? Which is pathogenic?

Answer 8

mold at ambient temperature (infectious form), yeast at body temperature (pathogenic), ex. Histoplasma, blastomyces

Question 9

is conidia infectious or pathogenic?

Answer 9

infectious

Question 10

how do we classify fungi?

Answer 10

1. spores/conidia, 2. hyphae structure

Question 11

name two variations in hyphae structure

Answer 11

1. septate (cross-walled) vs aseptate; 2. hyaline (no color) vs dematiaceous (brown-black)

Question 12

how to identify fungi

Answer 12

microscopic examination (wet prep) and/or culture isolation

Question 13

name one thing in the fungal cell wall, and one thing in the fungal cytoplasmic membrane

Answer 13

wall=chitin; membrane=sterols

Question 14

what do polyene antifungals disrupt?

Answer 14

cell membrane, through ergosterol binding and lysis

Question 15

what do pyrimidine analogue antifungals disrupt?

Answer 15

fungal DNA synthesis, through inhibition of thymidylate synthetase

Question 16

what do azole antifungals disrupt?

Answer 16

cell membrane, by inhibiting ergosterol production

Question 17

what do echinocandin antifungals disrupt?

Answer 17

cell wall, through inhibition of glucan synthetase

Question 18

what is the “penicillin” of antifungals?

Answer 18

fluconazole (free in Africa)

Question 19

what would you use for someone with fluconazole resistant fungal infection?

Answer 19

echinocandins (but they are expensive)

Question 20

what antifungal should be used for superficial skin/mucous membrane infections, and why?

Answer 20

fluconazole because oral, low toxicity, and inexpensive

Question 21

what is the treatment of choice for invasive fungal infection (CSF, lung, dimorphic)?

Answer 21

amphotericin B (liposomal) – polyene drug

Question 22

what are the downsides to amphotericin B?

Answer 22

parenteral only, high renal toxicity, expensive

Question 23

when would someone treat with echinocandins?

Answer 23

invasive candida, aspergillus, and pre-transplant prophylaxis (but IV only, expensive)

Question 24

for what particular fungal pathogen should echinocandins NOT be used?

Answer 24

cryptococcus

Question 25

what do pseudohyphae look like?

Answer 25

pinched off, see this is candida

Question 26

name three common infections from candida

Answer 26

oral thrush, vaginal yeast infection, diaper rash

Question 27

what are risk factors for invasive candida disease?

Answer 27

immunosuppression, neonates, solid organ transplant patients, prior antimicrobials, central venous catheter, ventilators, parenteral nutrition

Question 28

why is invasive candida so deadly?

Answer 28

often wrong, delayed, or no therapy because patients are treated with antibiotics, often results in negative culture, can't diagnose by serology, difficult to distinguish between colonization and infection