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Unit 3 Microbio > L23: Dermatomycoses > Flashcards

L23: Dermatomycoses Flashcards

1
Q

Cutaneous fungi (2)

A

Malassezia furfur

Hortaea werneckii

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2
Q

Dermatophytes (3)

A

Trichophyton
Microsporum
Epidermophyton

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3
Q

Environmental dermatophytes with sexual spores (2)

A

Microsporum

Trichophyton

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4
Q

Characteristics of dermatophytes

A

pathogenic fungi that require keratin for growth
do not infect mucosal surfaces
secrete keratinase

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5
Q

infective stage of dermatophytes

A

arthroconidium: spores

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6
Q

infected hairs exhibit fluorescence

A

ceratin species of microsporum

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7
Q

Visualize ______ in dead keratinized tissue to diagnose dermatophytes

A

hyphae

arthoconidia

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8
Q

Lab culture of dermatophytes

A

material under nails

sabouraud agar at room temperature 1-3 weeks

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9
Q

Dermatophyte test medium

A

allows for early detection: 3 days

fermentation of nitrogenous compounds preferred over carbohydrates: color change (alkaline pH): differential

Selective: cyclohexamide and abx

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10
Q

Identify trichophytin:

A

Galactomannan peptide
Crude antigen of dermatophytes
-CHO component: immediate response
-Peptide component: delayed response

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11
Q

10% potassium hydroxide

A

KOH

digests human tissue, leaves fungal components intact

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12
Q

Zoophilic

A

animal pathogens that may be transmitted to people

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13
Q

Antrophophilic

A

human transmission

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14
Q

geophilic

A

transmitted through soil to people

usually invade non-viable keratinized tissue

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15
Q

Where are dermatophytes most prevalent?

A

tropics

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16
Q

What do dermatophyte lesions look like?

A

Inflammed at edges, central clearing zone

hair loss with itching

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17
Q

Predisposed to dermatophyte infection

A

Nail trauma
HIV
DM
Immunosuppressive meds

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18
Q

Risk factors for dermatophyte infection

A

Communal bathing facilities
Immunocompromised
Cushing syndrome (increased cortisol interferes with inflammation)
Contact sports

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19
Q

Disseminated dermatophyte infection in HIV patients (2)`

A

T mentagrophytes

M canis

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20
Q

Arthrospores

A

fragment hyphal elements in hair, nails, outer skin
disseminate from one host to another (person-to-person)
survive in environment

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21
Q

Besides arthrospores, other ways to get a dermatophyte infection

A

micronidia (asexual spore)
macronidia (multicellular asexual spore)
sexual spores

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22
Q

Id reaction

A

allergic dermal reaction to fungal antigens occurring in areas devoid of organisms
most common in tinea pedis
sometimes a result of excessive treatments or pruritus

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23
Q

Id reaction treatment

A

treated as an allergy:
corticosteroids, antihistamines (systemic or topical)
wet compresses

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24
Q

what are spores susceptible to?

A

common disinfectants, chlorine, bleach, detergents

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25
Q

3 Trichophyton species

A

technically there are “5 major clinically relevant species”

  • T mentagrophytes*
  • T tonsurans*
  • T rubrum*
26
Q

Do trichophyton species fluoresce?

A

Not often

27
Q

Trichophyton macroconidia

A

pencil shaped, thin walls

28
Q

Trichphyton produce

A

spindle shaped hyphae
microconidia
macroconidia

29
Q

Most common cause of tinea capitis

A

Microsporum species

30
Q

Do microsporum fluoresce?

A

Yes, under a wood’s lamp

31
Q

Microsporum produce

A

Hyphae
Microconidia
Large, spindle shaped, thick walled, mulitcellular Macroconidia

32
Q

Tinea unguium aka

A

onychomycosis

nails

33
Q

Tinea cruris

A

jock itch

groin

34
Q

Most common causes to tinea capitis (3)

A

M canis
T metagrophytes
T tonsuranx

35
Q

Tinea capitis: trichophyton

A

endothrix

Insidee the hair follicle, causes alopecia

36
Q

Tinea capitis:microsporum

A

ectothrix

outside surface of the hair

37
Q

zoonotic tinea capitis

A

comes from puppies and kittens

38
Q

black dot ringworm

A

comes from broken follicles appearing as black dots

39
Q

most prevalents dermatophytoses

A

tinea pedis

40
Q

Predisposing factors to tinea corporus/cruris

A

DM
obesity
excessive perspiration

41
Q

Transmission of tinea corporus/cruris is both ____

A

direct

indirect: contact with objects: towels, clothing, bed linens

42
Q

For onychomycosis, treatment requires

A

systemic antifungals

culture: often candida

43
Q

what is tinea unguium sometimes mistaken for?

A

psoriasis

44
Q

Is candida a dermatophyte?

A

NO

It is a mycoses

45
Q

Most common opportunistic mycoses worldwide

A

candida species

46
Q

A parent yeast cell of candida can take on 3 different morphologies:

A
  1. Budding yeast
  2. Pseudohypha
  3. Germ tube
    - germ tube can differentiate into hyphae
47
Q

The most adhesive candida morphology

A

Germ tube

48
Q

Does candida have a lot a virulence factors?

A

NO

but all species are capable of attachment

49
Q

Whatcha gonna see on direct microscopic examination of candida?

A

Large “G+” cells
Yeast cells
Pseudohyphae
True hyphae

50
Q

Cultures for candida

A

Chromagar

Germ tubes: incubate in serum for 3 hours at 37 C

51
Q

Serology for candida

A

difficult, as it’s normal flora and a pt may have had prior exposure
low titers of antibody

52
Q

Tinea versicolor aka

A

malassezia furfur

53
Q

malassezia furfur morphology (under a microscope+KOH)

A

short unbranched hyphae + spherical cells = “spaghetti and meatballs”

54
Q

Liphilic growth factor

A

means it needs fat to grow- sebaceous glands

malassezia furfur

55
Q

malassezia furfur is most common in

A

tropics

young adults

56
Q

malassezia furfur appears as

A

depigmented or hyperpigmented skin
may enlarge
+/- dandruff

57
Q

Tinea negra aka

A

hortaea werneckii

58
Q

extreme halotolerant

A

hortaea werneckii

59
Q

hortaea werneckii morphology

A

dimorphic: can grow as yeast or mold

60
Q

hortaea werneckii looks like

A

a brownish lesion: produces melanin

Unit 3 Microbio (13 decks)

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