Fungi and protozoa

Question 1

main opportunistic fungal infections

Answer 1

• commensals: candida spp.
• environmental yeasts/molds: cryptococcus spp., pneumocystis jiroveci, aspergillus spp., Mucor spp.
• infection only if immunosuppressed!

Question 2

anti-fungal drugs and their targets

Answer 2

1. DNA Synthesis inhibitors - flucytosine
2. Ergosterol synthesis inhibitors - Allylamines, Azoles, morpholines, and polyenes
3. Beta glucan (cell wall) synthesis - Candins

Question 3

Flucytosine

Answer 3

anti-fungal drug,
replaces uracil in mRNA –> inhibits thymidilate synthase,
so blocks DNA synthesis

Question 4

Allylamines

Answer 4

class of fungicidal drugs, used topically;
block squalene –> lanosterol (=> ergosterol).
* esp. for: tinea (ringworm/athlete’s foot/jock itch)

Question 5

Azole

Answer 5

class of fungistatic drugs, used topically;
inhibits lanosterol –> ergosterol
* esp. for: dermatophytes

Question 6

Morpholines

Answer 6

class of anti-fungal drug,
inhibits Lanosterol --> ergosterol

Question 7

polyene

Answer 7

class of fungistatic drug, 
binds and blocks ergosterol into cell membrane; 
* toxic if binds to cholesterol!
***Amphotericin B = via IV, must be hospitalized administration and monitoring

Question 8

Candins

Answer 8

class of anti-fungal drug, 
blocks 1,3-B glucan synthesis for cell wall.

Question 9

Blastomyces dermatitidis

Answer 9

dimorphic fungus, found in SW and MW USA from rotting leaves, common spread from dogs.
Dx: rapid urine test
- nodular lesions with vesicles on top, pulmonary infection
Incubation: 45 days
* dissemination only if immunocompromised

Question 10

Exserohilum rostratum

Answer 10

fungus that (rarely) causes skin infections or endocarditis, 
from soil in warm, humid climates.

Question 11

Ringworm and associated infections

Answer 11

aka: tinea ___, = fungal infections by
- Trichophyton Rubrum/tonsurans
- Microsporum canis
- Epidermophyton floccosum (esp. unguium and cruris)
In hot/humid/damp environment, spread by fomites;
Dx: Scaly, itchy skin; ID on wet mount w/ KOH
* only on keratinized tissue.

Question 12

Malssezia globosa/furfur

Answer 12

opportunistic fungal infection, from normal skin flora;
Dx: fawn patches on back/chest
–> pulmonary infection or sepsis in immunocompromised
(ie: parenteral diet, stem cell transplant)
* no immune involvement!

Question 13

Histoplasma Capsulatum

Answer 13

Fungus common in MW USA, = common endemic infection;
Transmission: Aerosol, 1st from bats
–> “acute pulmonary histoplasmosis” = flu-like, self-resolving
—> skin lesions (hormonally linked)
* can be dormant and reactivated!

Question 14

Coccidiodes immitus

Answer 14

Fungal infection found in SW USA (~only), aka: Valley Fever;

• -> Rash (eryth. nodosum = type III hs), fever, cough, head&muscle ache
• –> skin lesions, joint infection w/ inflamm, pneumonia or meningitis

Question 15

Sporothric Schencki

Answer 15

fungal infection,

transmission: puncture wound or animals w/ lesions
- -> necrotic papule at inf. site,
- –> Open boils, pneumonia/TB (esp. if have COPD)
* systemic = only if immunocompromised.

Question 16

Candida albicans

Answer 16

opportunistic fungal (yeast) infection,
–> pasty discharge, vaginal itching, OR thrush
Also: - krusei
- glabrata fluconazole resistant
30-50% mortality if into bloodstream; = esp. mucocutaneous candidiasis

Question 17

Cryptococcus

Answer 17

opportunistic fungal infection found on West coast USA, 
from pigeon guano (poop), 
* has antiphagocytic capsule
--> granulomas/pulmonary infection
---> meningitis (high fatality) 
Dx: Rapid Ag test, yeast capsules in CSF

Question 18

pneumocystis jiroveci

Answer 18

opportunistic fungal infection, common 2nd inf. w/ HIV.

• -> pneumocystis (cyst-like protiens clog airway)
• –> NO disseminated form. (high fatality)
• • CHOLESTEROL = main membrane component here!!
    treatment: use trimeth/sulfm. (resistant to drugs targeting ergosterol!)

Question 19

Aspergillosis and Mycormycosis

Answer 19

2 fungi (molds) often found in damp, dark places (ie: basement);
Aspergillus - fumigatus/niger: inhaled,
–> invasive apergilloma.
Mucormycosis - mucor/rhizopus: inhaled/ingested/trauma,
–> severe tissue necrosis (ie: Joplin, MO)
* both = in immunocompromised (asthma, stress, HIV, etc.)