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Mycology > Superficial, Cutaneous, and Sub-Cutaneous Mycoses > Flashcards

Superficial, Cutaneous, and Sub-Cutaneous Mycoses Flashcards

1
Q

What are the main components of the fungal cell wall?

A

Glucans, chitin, fibrillar proteins, mannoproteins, ergosterol

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2
Q

Name the different types of fungal morphology

A

Yeasts, molds, dimorphic

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3
Q

Name the 3 dimorphic fungi that you need to know

A

Histoplasma capsulatum, Blastomyces dermatitides, Coccidiodes immitis

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4
Q

What is the metabolism of a fungus?

A

Heterotrophs!

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5
Q

What are the three fungal pathways of infection?

A

Contact, trauma, inhalation

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6
Q

Type I Hypersensitivity

A

Allergic Rhinitis

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7
Q

Type III Hypersensitivity

A

Farmer’s Lung

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8
Q

What does a wet mount with 10% KOH do?

A

Kills everything except for the fungi

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9
Q

What does staining with Lactophenol Cotton Blue accomplish?

A

Determines if the fungi are septate or aseptate

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10
Q

What does Sabouraud’s Agar accomplish?

A

Suppresses non-pathogenic fungi

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11
Q

What is serology used for?

A

Deep or systemic infections

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12
Q

Polyenes

A

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

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13
Q

Flucytosine (5-Fluorocytosine)

A

-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

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14
Q

What are the two types of azoles?

A

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

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15
Q

Azoles (MOA &Resistance)

A

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

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16
Q

Echinocandins

A

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

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17
Q

Allylamines

A

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

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18
Q

Who is Griseofulvin prescribed for?

A

Given orally for kids with ringworm. Messes with mitosis

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19
Q

What does Tolnaftate due?

A

Inhibits squalene epoxidase (A Allymine)

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20
Q

What is Tinea Versicolor caused by?

A

Malassezia furfur

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21
Q

What can Tinea Versicolor cause?

A

Seborrheic dermatitis (actually itches unlike original condition)

22
Q

How do you diagnose Tinea Versicolor?

A

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

23
Q

What is White Piedra caused by?

A

Trichosporon Cutaneum

24
Q

Does White Piedra damage the hair?

A

No

25
Q

What is a characteristic of White Piedra?

A

Grows well on Sabouraud’s agar

26
Q

How would you treat White Piedra?

A

Topical azoles

27
Q

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

A

1) Trichophyton
2) Epidermophyton
3) Microsporum

28
Q

What are the four species of Trichophyton?

A

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

29
Q

What are some characteristics of Trichophyton?

A

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

30
Q

What are some characteristics of Epidermophyton?

A

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

31
Q

What are the three species of Microsporum?

A

1) Canis
2) Gypseum
3) Fulvum

32
Q

What are some characteristics of Microsporum?

A

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

33
Q

What two organisms cause Tinea Corporis (ring worm)?

A

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

34
Q

What is the most common Dermatophyte?

A 
Tinea Pedis (Athlete's Foot)
-Can progress to the toenail
35
Q

Describe a major characteristic of Tinea Cruris (jock itch)

A

It does not affect the scrotum!

36
Q

Ectothrix

A

Microsporum. Grows outside of hair shaft.

37
Q

Endothrix

A

Trichophyton. Grows inside of hair shaft.

38
Q

Describe the characteristics of Tinea Capitis and Barbae

A

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
39
Q

Tinea Unguium

A

Caused by T. rubrum but can be caused by other organsims

-Nails become thickened, discolored, friable, deformed

40
Q

How would you diagnose a Dermatophytosis?

A
  • KOH preps
  • Microsporum grows under Wood’s lamp
  • Endothrix vs. Ectothrix
  • Inoculate on Sabouraud’s agar
41
Q

How would you treat a Dermatophytosis?

A

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

42
Q

Where do the organisms that cause a subcutaneous mycosis live?

A

Soil and vegetation

43
Q

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

A

Trauma

44
Q

What is the typical course of a subcutaneous mycosis?

A

Chronic and insidious

45
Q

What is Lymphocutaneous Sporotrichosis caused by?

A

Sporothrix schenckii

46
Q

Describe the morphology of Lymphocutaneous Sporotrichosis

A

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

47
Q

What is Lymphocutaneous Sporotrichosis associated with?

A
  • Warm climates (Japan, N and S America)
  • Associated with trauma (rose thorns)
  • Also associated with armadillos and cats
48
Q

Describe the pathogenesis of Sporotrichosis

A
  • Primary lesion is a small ulcerating lesion

- Secondary lesions are subcutaneous nodules that appear two weeks later and follow lymphatic drainage

49
Q

What is fixed Sporotrichosis?

A
  • Occurs in Mexico

- A single non-lymphangitic nodule

50
Q

How would you diagnose Sporotrichosis?

A

-Culture pus from ulcerated nodule or infected tissue

51
Q

How would you treat Sporotrichosis?

A
  • Oral Itraconazole is the current drug of choice

- Classic treatment was oral KI

Mycology (5 decks)

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