Superficial, Cutaneous, and Sub-Cutaneous Mycoses

Question 1

What are the main components of the fungal cell wall?

Answer 1

Glucans, chitin, fibrillar proteins, mannoproteins, ergosterol

Question 2

Name the different types of fungal morphology

Answer 2

Yeasts, molds, dimorphic

Question 3

Name the 3 dimorphic fungi that you need to know

Answer 3

Histoplasma capsulatum, Blastomyces dermatitides, Coccidiodes immitis

Question 4

What is the metabolism of a fungus?

Answer 4

Heterotrophs!

Question 5

What are the three fungal pathways of infection?

Answer 5

Contact, trauma, inhalation

Question 6

Type I Hypersensitivity

Answer 6

Allergic Rhinitis

Question 7

Type III Hypersensitivity

Answer 7

Farmer’s Lung

Question 8

What does a wet mount with 10% KOH do?

Answer 8

Kills everything except for the fungi

Question 9

What does staining with Lactophenol Cotton Blue accomplish?

Answer 9

Determines if the fungi are septate or aseptate

Question 10

What does Sabouraud’s Agar accomplish?

Answer 10

Suppresses non-pathogenic fungi

Question 11

What is serology used for?

Answer 11

Deep or systemic infections

Question 12

Polyenes

Answer 12

Amphotericin B (oral) and Nystatin (topical)
Mode of Action: Binds ergosterol and forms pores in fungal cell membranes
Resistance: Reduce amount of ergosterol or replace ergosterol with fecosterol

Question 13

Flucytosine (5-Fluorocytosine)

Answer 13

-Converted to 5-FU by cytosine deaminase and brought into the cell via permease
-MOA: Competes with uracil to block RNA synthesis and 5-FUMP interferes with thymidylate synthase to block DNA synthesis
Resistance: Block cytosine deaminase and permease

Question 14

What are the two types of azoles?

Answer 14

Imidiazoles: Ketoconazole and Miconazole
Triazoles: Fluconazole, Itraconazole, Voriconazole

Question 15

Azoles (MOA &Resistance)

Answer 15

MOA: Inhibits 14-alpha demethylase which converts lanosterol to ergosterol (lano is toxic)
Resistance: Alter 14-alpha demethylase or efflux drugs out of the cell faster than they come in

Question 16

Echinocandins

Answer 16

MOA: Interfere with beta 1,3 glucans
Resistance: Target alteration

Question 17

Allylamines

Answer 17

MOA: Inhibits squalene epoxidase needed to make ergosterol
***Works very well for skin infections
Resistance: Efflux from cells

Question 18

Who is Griseofulvin prescribed for?

Answer 18

Given orally for kids with ringworm. Messes with mitosis

Question 19

What does Tolnaftate due?

Answer 19

Inhibits squalene epoxidase (A Allymine)

Question 20

What is Tinea Versicolor caused by?

Answer 20

Malassezia furfur

Question 21

What can Tinea Versicolor cause?

Answer 21

Seborrheic dermatitis (actually itches unlike original condition)

Question 22

How do you diagnose Tinea Versicolor?

Answer 22

1) Spaghetti and meatballs appearance on KOH
2) Fluoresces yellow under Wood’s lamp
3) Culture on mycologic agar&olive oil

Question 23

What is White Piedra caused by?

Answer 23

Trichosporon Cutaneum

Question 24

Does White Piedra damage the hair?

Answer 24

No

Question 25

What is a characteristic of White Piedra?

Answer 25

Grows well on Sabouraud's agar

Question 26

How would you treat White Piedra?

Answer 26

Topical azoles

Question 27

What are the three organisms that cause Cutaneous Mycoses (Dermatophytoses)?

Answer 27

1) Trichophyton 2) Epidermophyton 3) Microsporum

Question 28

What are the four species of Trichophyton?

Answer 28

1) Rubrum 2) Mentagorophytes 3) Tonsurans 4) Verrucosum

Question 29

What are some characteristics of Trichophyton?

Answer 29

May see spiral hyphae. Microscopically identified by their condida. Macrocondida are rare.

Question 30

What are some characteristics of Epidermophyton?

Answer 30

Macroconidia are smooth-walled and in cluster. Microcondidia are rare. Does not infect hair!

Question 31

What are the three species of Microsporum?

Answer 31

1) Canis 2) Gypseum 3) Fulvum

Question 32

What are some characteristics of Microsporum?

Answer 32

Macroconidia are large, rough, and thick walled. Microconidia are rare. Does not infect nails!

Question 33

What two organisms cause Tinea Corporis (ring worm)?

Answer 33

T. rubrum (anthropomorphic) and M. canis (zoophilic)

Question 34

What is the most common Dermatophyte?

Answer 34

``` Tinea Pedis (Athlete's Foot) -Can progress to the toenail ```

Question 35

Describe a major characteristic of Tinea Cruris (jock itch)

Answer 35

It does not affect the scrotum!

Question 36

Ectothrix

Answer 36

Microsporum. Grows outside of hair shaft.

Question 37

Endothrix

Answer 37

Trichophyton. Grows inside of hair shaft.

Question 38

Describe the characteristics of Tinea Capitis and Barbae

Answer 38

Live off of the hair shaft unlike T. cutaneum - Dull grey patches of alopecia, scaling, and itching - Kerion may form in response to infection with zoophilic dermatophyte

Question 39

Tinea Unguium

Answer 39

Caused by T. rubrum but can be caused by other organsims | -Nails become thickened, discolored, friable, deformed

Question 40

How would you diagnose a Dermatophytosis?

Answer 40

- KOH preps - Microsporum grows under Wood's lamp - Endothrix vs. Ectothrix - Inoculate on Sabouraud's agar

Question 41

How would you treat a Dermatophytosis?

Answer 41

1) Topical azoles work very well 2) Oral azoles 3) Terbinafine (oral&topical) 4) Partial surgical removal of nails

Question 42

Where do the organisms that cause a subcutaneous mycosis live?

Answer 42

Soil and vegetation

Question 43

What does a subcutaneous mycosis require in order to bypass intact skin?

Answer 43

Trauma

Question 44

What is the typical course of a subcutaneous mycosis?

Answer 44

Chronic and insidious

Question 45

What is Lymphocutaneous Sporotrichosis caused by?

Answer 45

Sporothrix schenckii

Question 46

Describe the morphology of Lymphocutaneous Sporotrichosis

Answer 46

At ambient temp it's got septate hyphae and conidia arranged in a flower pattern with thin conidiophores At body temp its a pleomorphic yeast

Question 47

What is Lymphocutaneous Sporotrichosis associated with?

Answer 47

- Warm climates (Japan, N and S America) - Associated with trauma (rose thorns) - Also associated with armadillos and cats

Question 48

Describe the pathogenesis of Sporotrichosis

Answer 48

- Primary lesion is a small ulcerating lesion | - Secondary lesions are subcutaneous nodules that appear two weeks later and follow lymphatic drainage

Question 49

What is fixed Sporotrichosis?

Answer 49

- Occurs in Mexico | - A single non-lymphangitic nodule

Question 50

How would you diagnose Sporotrichosis?

Answer 50

-Culture pus from ulcerated nodule or infected tissue

Question 51

How would you treat Sporotrichosis?

Answer 51

- Oral Itraconazole is the current drug of choice | - Classic treatment was oral KI