Wk16D1 Fungi Basics

Question 1

8 Virulence factors

Answer 1

Cell wall, capsules, proteases, lipases, toxins, melanin, adhesins, biofilms

Question 2

Fungal plasma membrane and cell wall components.

Answer 2

Plasma membrane contains ergosterol.

Cell wall contains chitin (polysaccharide), other polysaccharides (B-glucan), and other density-based layersd

Question 3

What is clinical significance of ergosterol?

Answer 3

Not found in mammalian cells, so a drug target.

Ergosterol synthesis or in membrane

Question 4

Lab test method for identifying Candida albicans and Cryptococcus neoformans

Answer 4

Candida albicans = + germ tube test

Cryptococcus neoformans - India stain (negative stain)

Question 5

Lab methods to diagnose cryptococcal meningitis (as well as therapeutic monitoring)

Answer 5

Culture of spinal fluid or sputum. India ink, latex bead agglutination, CSF titer decreases w/ effective therapy. Fontana Masson stain (melanin)

Question 6

How does morphology of Blastomyces dermatitidis and HIstoplasma capsulatum differ as they appear in host and environment?

Answer 6

In general, dimorphic are moulds @ 28-30C and yeast @ 37 (except coccidiodes = spherules)

Question 7

Polyenes MOA, Resistance, Example

ON SUMMATIVE!!!

Answer 7

Bind ergosterol, disrupting membrane
Ergosterol downregulation/ replacement/ reorientation
AmB IV, Nystatin oral/topical

Question 8

Azoles MOA, Example

ON SUMMATIVE!!!

Answer 8

Inhibit C. P450 demethylation of ianosterol (ergo synth)

Imidazoles (ketoconazole) and triazoles (IVF, itra/vori/flu)

Question 9

Echinocandins MOA, Resistance, Example

Answer 9

Noncompetitively inhibit B1,3-glucan synthase (cell wall)
Target mod/downreg
-fungins (capso/mica/anidula)
Use for candidiasis

Question 10

Allyamines MOA, Resistance, Example

Answer 10

Inhibit squalene epoxidase (ergo synth, squalene accumulation)
Target mod/upregulation, penetration
-fines (nafti/terbina[oral])…H-PHOBIC
Used in dermatophytosis

Question 11

5-fluorocysteine MOA, Resistance

Answer 11

Nucleic acid synth
Rapid resistance
Limited spectrum of activity

Question 12

What are yeasts? How do yeasts reproduce?

Answer 12

Unicellular and round

mitosis: budding or fission

Question 13

What are moulds? How do moulds reproduce?

Answer 13

Multicellular and filamentous, hyphae+septa

Use spores + conidia

Question 14

What’s are the 2 main forms of fungi? What is an example of an alternative form?

Answer 14

Yeasts, Moulds

Spherules: Coccidiodes

Question 15

Manifestations of Candidiasis and Ecology

Answer 15

Mostly Candida albicans. Yeast infection, thrush, but can infect all organs.
Found in most people in GI/GU tracts. Birth canal, dentures, Abx, immunosuppression, pregnancy

Question 16

Is Candidiasis contagious? Who gets Candidiasis?

Answer 16

Not usually though it can be found in environment. Typically etiology is from individuals flora.
Patients with neutropenia, diminished phagocytosis, diminished cell mediated immunity (mucocutaneous involvement)
PSEUDOPHYPHAE
String of pearls in retina

Question 17

What is a mucocutaneous area? What might it indicate?

Answer 17

Where mucus becomes skin (lips, nostril, conjunctiva, vagin, urethra, anus)…candidiasis there indicative of cell-mediated immunity aka CD4 defect.

Question 18

Kneejerk reaction: PIGEON Droppings
Organisms
Diseases
Also, EUCALYPTUS
Diagnosis

Answer 18

CRYPTOCOCCOSIS!!! C. neoformans/gattii/grubbii with HUGE galactoxylomannan capsule (negative immunomodulator, negative stain)
Pneumonia (may evade xray)
Meningitis (esp. in collagen disease patients)
Not dimorphic
Eucalyptus - gattii, immuno-competent peeps
CrAg from CSF

Question 19

Histoplasmosis

Answer 19

Intracellular (HISTiOcytes!), Tornado Alley area, often in AIDS patients. Pigeon, Bird/bat droppings. Mimics TB.
Treatment: liposomal amphotericin B, Itraconazole
Fistula
Urine ag test
Coin lesion

Question 20

Blastomycosis

Answer 20

Wider, norther Tornado alley. Mimic TB w/ SKIN+bone lesions. Yeast has broad base bud. DOGS and BEAVER DAM (wet wood). Hyphae pair-shaped

Question 21

Coccidioidomycosis

Answer 21

SW USA and below. C. immitis/posadasii. Filipinos. Filament in environment. Coccidiodin skin test. Desert bumps/rheumatism.
Treat with triazoles then amphotericin B
Meningitis: lifelong fluconazole

Question 22

Aspergillosis

Answer 22

Worldwide
Organ transplants, burns, foreign bodies
Angioinvasive hyphae V shaped branches
Diagnose w/ Galactomannan or Beta-D-glucan
Only mold, forms moving fungus ball
ABPA mimics asthma

Question 23

Uncontrolled Diabestes

Answer 23

Mucor and Rhizopus

Hyphae at right angles