Microbiology-Mycoses

Question 1

What are the two categories of fungi?

Answer 1

Yeasts (single cell), Molds (multicellular)

Question 2

Fungi are eukaryotes, however, their cell wall differs greatly from our plasma membranes. What is different?

Answer 2

Chitin (polysaccharide w/N-acetylglucosamine), glucans, and ergosterol (like cholesterol)

Question 3

What is the primary target of anti fungal drugs?

Answer 3

Ergosterol in the cell membrane of fungi

Question 4

How do most yeast replicate?

Answer 4

Budding

Question 5

Instead of unique cells, how is mold structured?

Answer 5

Hyphal compartments continually grow outward.

Question 6

How does fungal mold replicate?

Answer 6

Hyphae grow up from the mold and dissociate into spores.

Question 7

How is fungal species determined?

Answer 7

Spore shape

Question 8

How can you tell when a spore starts germinating?

Answer 8

Germ-tube.

Question 9

How is fungus identified microscopically?

Answer 9

KOH dissolves surrounding cells so you can see fungus, silver staining and Calcofour white staining

Question 10

What type of agar do you grow fungus on?

Answer 10

Sabouraud’s agar. It inhibits bacterial growth.

Question 11

What are the three main anti fungal agents?

Answer 11

Azoles (ergosterol synthesis inhibitor), Polyenes/Amphotericin (binds ergosterol and forms pores), Echinocandins (inhibit beta-glucan synthesis for cell wall)

Question 12

What immunity cells are key in preventing fungal infections?

Answer 12

Endothelial cells (recognizes beta-glucan’s dectin-1 and releases defensins), neutrophils, Th1 and Th17 cells.

Question 13

How are fungus infections categorized clinically?

Answer 13

Superficial, Cutaneous, Subcutaneous, Systemic and Opportunistic

Question 14

What yeast does Selsun Blue target?

Answer 14

Malassezia globosa

Question 15

What yeast causes Pityriasis versicolor?

Answer 15

Malassezia furfur.

Question 16

What disease culture can be enhanced by addition of oil?

Answer 16

Pityriasis versicolor

Question 17

Pityriasis versicolor is not resolved unless treated. What treatments help resolve the infection?

Answer 17

Selenium shampoo or topical azole

Question 18

A skin scraping shows this spaghetti and meatball appearance. What is the likely fungus?

Answer 18

Pityriasis versicolor

Question 19

What are the common assailants of cutaneous mycoses?

Answer 19

Dermatophytes. The invade the stratum corneum, nails and hair.

Question 20

What is this infection called?

Answer 20

Tinea capitis

Question 21

What is this infection called?

Answer 21

Tinea pedis. Typically presents in moccasin distribution and desquamation.

Question 22

How do you treat this infection?

Answer 22

Tinea unguium is treated with oral antifungals for months. Once fungal infections get into hair and nails you can’t use topical drugs anymore.

Question 23

What type of fungal infections often require surgical interventions combined with medical treatments?

Answer 23

Subcutaneous mycoses. These are most often acquired by forced trauma.

Question 24

What is the most common subcutaneous mycoses in the US?

Answer 24

Sporotrichosis

Question 25

Your neighbor is out in her garden and is poked by a rose bush. A couple of weeks later she gets a nodule where she was poked. A few months later she has nodules with linear spacing up her arm. What is your diagnosis?

Answer 25

Sporotrichosis

Question 26

How does the immune system respond to sporotrichosis?

Answer 26

Granuloma formation and eosinophils

Question 27

You investigate a patient’s fungal infection by growing the fungus. You observe dematiaceous (pigmented) mold. What is the likely fungus?

Answer 27

Chromomycosis

Question 28

Why is it important to differentiate eumycotic mycetoma from actinomycotic mycetoma?

Answer 28

Actinomycotic mycetoma can be easily treated with antibiotics and eumycotic mycetoma often requires amputation.