Micro U2 L5. Flashcards
Dermatophytoses: what is it caused by and what do it infect?
dermatophytes = infects skin, hair, nails
Which genera of dermatophytoses can you contract from pets?
microsporum
What are the three genera of dermatophytoses?
epidermophyton, trichophyton, microsporum
Where do dermatophytoses cause infection?
warm human area - cause inflamed circular border of papules and/or vesicles
What does hypersensitivity to dermatophytid (circulating fungal antigen) cause?
vesicles on finger
How is diagnosis of dermatophytoses made?
PPD with trichophytin; microscopic exam; culture; wood’s lamp
How is microscopic exam of dermatophytoses done?
- scrape affected skin/nail 2. treat with 10% KOH 3. examine remains for hyphae/spores
What type of agar is used to dermatophytoses culture?
sabouraud’s agar at room temp
What does dermatophytoses show when examined under wood’s lamp?
fluorescence
Treatment of dermatophytoses
topical antifungal cream (terbinafine, undecylenic acid, miconazole, tolnaftate; oral griseofulvin; keep skin dry and cool
Tinea versicolor organism
malassezia furfur (normal flora - overgrowth)
What does tinea versicolor cause?
superficial skin infection (only cosmetic), hypo pigmented areas with slight scaling/itching - most frequent in hot, humid weather
How is diagnosis of tinea versicolor made?
take skin scrapings and treat with 10% KOH; examine microscopically for mix of budding yeasts and hyphae
Treatment of tinea versicolor
topical miconazole
Tinea Nigra organism
cladosporium werneckii
Tinea Nigra pathogenesis
spores in soil that enter injury; germinate keratinized skin layers; generate a brown pigment (resembles melanoma)
Where is tinea nigra seen?
South US
How is diagnosis of tinea nigra made?
skin scarpings, culture on sabouraud’s, treat with 10% KOH - examine microscopically for hyphae
Tinea Nigra treatment
topical keratolytic agent (salicyclic acid) plus topical azole
What are the cutaneous mycoses?
dermatophytoses, tinea nigra, tinea versicolor
How are the subcutaneous mycoses introduced?
by trauma exposing subcutaneous tissue to soil or vegetation
Sporotrichosis organism
thermally dimorphic, found in vegetation - seen in gardeners
Pathogenesis of sporotrichosis
introduced by thorn puncture -> yeast grow at site and form painless pustule/ulcer -> draining lymphatics form nodules -> symptoms wane and wax (disseminated in immunosuppressed)
Sporotrichosis exam
painless pustule or ulcer hand or arm, history of gardening and uneffective antibacterial treatment
Labs for sporotrichosis
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)
Treatment of sporotrichosis
itraconazole (3-6 months)
Chromomycosis organism
dermatiaceous fungi: fonsecaea, phialophora, cladosporium
Where is chromomycosis found?
soil in tropics
What color are conidia or hyphae of chromomycosis?
gray or black
Pathogenesis of chromomycosis
introduced into legs/feet with injury -> gradually progressive subcutaneous disease -> granulomas form as immune system attempts to contain
Diagnosis of chromomycosis
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)
Treatment of chromomycosis
oral flucytosine or thiabendazole 6 mo. min; local surgery
Mycetoma oraganism
petriellidium or madurella
How is mycetoma contracted?
soil through wounds
What is seen on exam of mycetoma?
replicating fungi form abscesses; pus containing compact colored granules forms and drains through local sinuses
What does mycetoma appear similar to? How are they differentiated?
actinomycosis - need to measure filamentous structures on stained slides (mycetoma will be larger)
Mycetoma treatment
attempt antibiotic and anti fungal therapy (oral azalea plus IV amphotericin B); surgical excision of abscesses necessary usually
Where is mycetoma found?
tropical areas
What are the subcutaneous mycoses?
sporotrichosis, chromomycosis, mycetoma
Candidiasis
an opportunistic cutaneous mycosis
Candidiasis primary organism
candida albicans
What are common symptoms of candidiasis overgrowth?
thrush, vaginitis, esophagitis, diaper rash, chronic mucocutaneous candidiasis
How does candidiasis appear on microscope?
oval yeast with single bud, may also appear as pseudohyphae
Virulence factors for candidiasis
adhesins, acid proteases, phenotypic switching
What is a predisposition for thrush? Vaginitis?
thrush: steroid inhalers for asthma; vaginitis: antibiotics, diabetes
Folliculitis
boil at the base of hair follicle seen in candidiasis
When does systemic candidiasis appear
AIDS, IL-17 deficient
Treatment of candidiasis
begin with symptoms on outside of body - add more as overgrowth becomes more serious
Candidiasis exam
rash, wet, itch surfaces; relevant predisposition
Candidiasis lab
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
