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DERM 1 > Derm Fungi > Flashcards

Derm Fungi Flashcards

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Dermatology Board Prep flashcards
1
Q

What is the most common dermatophyte fungus?

A

Trichophyton rubrum

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2
Q

What is the causal agent behind Tinea nigra?

A

Hortae werneckii

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2
Q

What is the most important virulence factor of the tineas?

A

keratinases to get through the stratum corneum

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3
Q

Which mycetoma granules are black?

A

M. grisea and E. jeanselmei

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4
Q

Why is tinea versicolor a misnomer for pityriasis versicolor?

A

Tinea describes ringworm type infections, Malassezia furfur is NOT a ringworm

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5
Q

What is unique of the cell walls of Hortae werneckii?

A

They are melanized, it is a dematiaceous fungus

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6
Q

Where do most of the subcutaneous mycoses come from?

A

soil

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7
Q

Who would be most at risk of a dermatophyte becoming a chronic issue?

A

Can happen in anyone but HIV and IC

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7
Q

What 3 bugs should be on the differential for “jock itch”?

A

Erythrasma = Corynebacterium minutissimum; Tinea cruis, and candida

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8
Q

Where is the most likely location of hyphae in a tinea infection?

A

Stratum corneum; these are dermatophytes

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9
Q

Which dermatophytoses are most common in A) Men and B) Women?

A

A) tinea capitis, tinea pedis, and tinea cruis B) tinea unguinum

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11
Q

What does Malassezia furfur look like on Wood’s lamp? On KOH?

A

Wood’s lamp = fluoresce bright yellow; KOH = spaghetti and meatballs

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11
Q

How does Sporothrix spread?

A

along the chain of lymphatics

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11
Q

Which causal agent of a mycetoma may disseminate in HIV or IC pts?

A

P. boydii (white granules)

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12
Q

When a person has a mycetoma, which two organisms are most likely to cause a superinfection?

A

staph and strep (NF of the skin = most likely)

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13
Q

T/F: both Piedraia hortae and Hortae werneckii are dematiaceous fungi?

A

True these are black piedra and tinea nigra, respectively

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14
Q

What kind of systemic infections can Trichosporon cause? What enzyme is it positive for in the lab?

A

Endocarditis of prosthetic valve or on native valve if IVDU; urease

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15
Q

How do you get Sporothrix schencki? What area of the body is most commonly involved?

A

Usually from a thorn prick, often the hands

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15
Q

How do you get a chromoblastomycosis?

A

generally in tropical and subtropical areas on FEET exposed to infected soil? Agricultural workers and mine workers

17
Q

How is the location of white piedra different from that of black piedra?

A

White piedra is facial, axillary, and pubic hair whereas black piedra is only on the face and scalp

19
Q

What causes white piedra? Black piedra?

A

White piedra = trichosporon spp; black piedra = piedraia hortae

20
Q

What is the difference in appearance between endothrix lesions and ectothrix lesions?

A

Endothrix = fungi inside hair shaft, hair breaks and does not leave black dots; Ectothrix = fungi outside of hair, hair breaks and leaves little black dots

22
Q

Name the 3 major dermatophytes

A

Microsporum, trichophyton, and epidermophyton floccosum

23
Q

What are the two main agents to cause mycetoma (starred organisms)?

A

Actinomyces and Nocardia

24
Q

What is the difference between dermatophytoses and dermatomycoses?

A

Dermatophytoses are superficial cutaneous infections that only invade superficial layers; Dermatomycoses are similar but they go deeper than just the epidermis

25
Q

What is a kerion?

A

an intense, painful, and boggy suppurative reaction often on the back of the neck and associated with cervical lymphadenopathy.

26
Q

What disease may occur with Malassezia furfur in the presence of a catheter?

A

Catheter Associated Sepsis

26
Q

What is the danger of tinea pedis? Why does the normal flora change?

A

Secondary infection from itching and–the normal flora changes because there are antibiotics produced by the fungus, this may also impact the secondary infection risk

27
Q

How would you differentiate between erythrasma and tinea cruis?

A

erythrasma = corynebacterium minutissimum fluoresces coral red with Wood’s lamp, tinea cruis does not fluoresce

28
Q

Which mycetoma granules are white?

A

Pseudallescheria boydii

29
Q

What are the names for the asexual and sexual forms of pityriasis versicolor?

A

Asexual = Malassezia furfur; Sexual = Pityrosporum orbiculare

30
Q

What is the most common zoophilic cause of tinea capitis worldwide?

A

Microsporum canis

32
Q

What is a dermatophytid?

A

It is a secondary rash to the dermatophyte, it is caused by the immune system so there are no fungi present

33
Q

Name the 4 superficial fungi (not the dermatophytes)?

A

Malassezia furfur (pityriasis versicolor); Horatea werneckii (tinea nigra); Trichosporon spp. (white piedra); Piedraia hortae (black piedra)

35
Q

What is the most common mode of transmission for a systemic mycosis?

A

respiratory (i.e. coccidiodes etc.)

36
Q

What immune response is needed to control Candidal infections?

A

T cell

37
Q

What is contained in the granules of a Mycetoma?

A

microcolonies of the agent embedded

38
Q

How do you get a mycetoma? What kind of inflammation?

A

Traumatic inoculation; granulomatous (subset of chronic)

39
Q

How would you differentiate between tinea cruis and candida for jock itch?

A

Candida affects both the scrotum and thigh; Tinea cruis only affects the thigh? Yes I’m sure never in the history of the world has tinea cruis ventured to the scrotum

40
Q

How do you grow Malassezia furfur? What is the likely significance of the fact that lesions occur in the distribution of sebaceous glands?

A

On solid media with olive oil since it requires long chain fatty acids to grow; sebum contains fatty acids!

41
Q

How would you differentiate between the two causes of tinea capitis that fluoresce?

A

HISTORY, Microsporum canis is from an animal and Microsporum andouini is from a human

42
Q

What is the most likely cause of tinea capitis in the U.S?

A

Trichophyton tonsurans

43
Q

Which mycetoma granules are dark red to black?

A

M. mycetomatis

44
Q

What is the name given to pigmented fungal cells in the pustules of a chromoblastomycosis?

A

Medlar body

45
Q

What are some ways (4) that the hyphal form of Malassezia furfur can be induced?

A

Increased temperature, high humidity, greasy skin (teens), hyperhidrosis

46
Q

What does it mean for a fungus to be dematiaceous?

A

The hyphae and/or spores are darkly pigmented because they contain melanin granules

DERM 1 (7 decks)

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