Micro U2 L5. Flashcards

1
Q

Dermatophytoses: what is it caused by and what do it infect?

A

dermatophytes = infects skin, hair, nails

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2
Q

Which genera of dermatophytoses can you contract from pets?

A

microsporum

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3
Q

What are the three genera of dermatophytoses?

A

epidermophyton, trichophyton, microsporum

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4
Q

Where do dermatophytoses cause infection?

A

warm human area - cause inflamed circular border of papules and/or vesicles

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5
Q

What does hypersensitivity to dermatophytid (circulating fungal antigen) cause?

A

vesicles on finger

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6
Q

How is diagnosis of dermatophytoses made?

A

PPD with trichophytin; microscopic exam; culture; wood’s lamp

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7
Q

How is microscopic exam of dermatophytoses done?

A
  1. scrape affected skin/nail 2. treat with 10% KOH 3. examine remains for hyphae/spores
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8
Q

What type of agar is used to dermatophytoses culture?

A

sabouraud’s agar at room temp

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9
Q

What does dermatophytoses show when examined under wood’s lamp?

A

fluorescence

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10
Q

Treatment of dermatophytoses

A

topical antifungal cream (terbinafine, undecylenic acid, miconazole, tolnaftate; oral griseofulvin; keep skin dry and cool

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11
Q

Tinea versicolor organism

A

malassezia furfur (normal flora - overgrowth)

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12
Q

What does tinea versicolor cause?

A

superficial skin infection (only cosmetic), hypo pigmented areas with slight scaling/itching - most frequent in hot, humid weather

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13
Q

How is diagnosis of tinea versicolor made?

A

take skin scrapings and treat with 10% KOH; examine microscopically for mix of budding yeasts and hyphae

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14
Q

Treatment of tinea versicolor

A

topical miconazole

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15
Q

Tinea Nigra organism

A

cladosporium werneckii

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16
Q

Tinea Nigra pathogenesis

A

spores in soil that enter injury; germinate keratinized skin layers; generate a brown pigment (resembles melanoma)

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17
Q

Where is tinea nigra seen?

A

South US

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18
Q

How is diagnosis of tinea nigra made?

A

skin scarpings, culture on sabouraud’s, treat with 10% KOH - examine microscopically for hyphae

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19
Q

Tinea Nigra treatment

A

topical keratolytic agent (salicyclic acid) plus topical azole

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20
Q

What are the cutaneous mycoses?

A

dermatophytoses, tinea nigra, tinea versicolor

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21
Q

How are the subcutaneous mycoses introduced?

A

by trauma exposing subcutaneous tissue to soil or vegetation

22
Q

Sporotrichosis organism

A

thermally dimorphic, found in vegetation - seen in gardeners

23
Q

Pathogenesis of sporotrichosis

A

introduced by thorn puncture -> yeast grow at site and form painless pustule/ulcer -> draining lymphatics form nodules -> symptoms wane and wax (disseminated in immunosuppressed)

24
Q

Sporotrichosis exam

A

painless pustule or ulcer hand or arm, history of gardening and uneffective antibacterial treatment

25
Q

Labs for sporotrichosis

A

tissue speciment - round or cigar-shaped budding yeasts - culture at room temp (hyphae with oval conidia in clusters at tip of slender conidiophores (look like daisies)

26
Q

Treatment of sporotrichosis

A

itraconazole (3-6 months)

27
Q

Chromomycosis organism

A

dermatiaceous fungi: fonsecaea, phialophora, cladosporium

28
Q

Where is chromomycosis found?

A

soil in tropics

29
Q

What color are conidia or hyphae of chromomycosis?

A

gray or black

30
Q

Pathogenesis of chromomycosis

A

introduced into legs/feet with injury -> gradually progressive subcutaneous disease -> granulomas form as immune system attempts to contain

31
Q

Diagnosis of chromomycosis

A

exam: wartlike dark colored lesions/crusting abscesses extendign along lymphatics. lab: tissue specimen with dark brown, round fungal cells INSIDE leukocytes or giant cells (granuloma response)

32
Q

Treatment of chromomycosis

A

oral flucytosine or thiabendazole 6 mo. min; local surgery

33
Q

Mycetoma oraganism

A

petriellidium or madurella

34
Q

How is mycetoma contracted?

A

soil through wounds

35
Q

What is seen on exam of mycetoma?

A

replicating fungi form abscesses; pus containing compact colored granules forms and drains through local sinuses

36
Q

What does mycetoma appear similar to? How are they differentiated?

A

actinomycosis - need to measure filamentous structures on stained slides (mycetoma will be larger)

37
Q

Mycetoma treatment

A

attempt antibiotic and anti fungal therapy (oral azalea plus IV amphotericin B); surgical excision of abscesses necessary usually

38
Q

Where is mycetoma found?

A

tropical areas

39
Q

What are the subcutaneous mycoses?

A

sporotrichosis, chromomycosis, mycetoma

40
Q

Candidiasis

A

an opportunistic cutaneous mycosis

41
Q

Candidiasis primary organism

A

candida albicans

42
Q

What are common symptoms of candidiasis overgrowth?

A

thrush, vaginitis, esophagitis, diaper rash, chronic mucocutaneous candidiasis

43
Q

How does candidiasis appear on microscope?

A

oval yeast with single bud, may also appear as pseudohyphae

44
Q

Virulence factors for candidiasis

A

adhesins, acid proteases, phenotypic switching

45
Q

What is a predisposition for thrush? Vaginitis?

A

thrush: steroid inhalers for asthma; vaginitis: antibiotics, diabetes

46
Q

Folliculitis

A

boil at the base of hair follicle seen in candidiasis

47
Q

When does systemic candidiasis appear

A

AIDS, IL-17 deficient

48
Q

Treatment of candidiasis

A

begin with symptoms on outside of body - add more as overgrowth becomes more serious

49
Q

Candidiasis exam

A

rash, wet, itch surfaces; relevant predisposition

50
Q

Candidiasis lab

A

exudate or tissue samples: budding yeasts and psudohyphae (gram-positive - visualized by calcofluor-white stain) - culture: large colonies similar to bacterial on agar - in serum = germ tubes