Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
68 Cards in this Set
- Front
- Back
|
What is the significance of superficial mycoses?
|
Usually only apparent when become a cosmetic problem; no host response because are remote from living tissue.
|
|
|
Name the superficial mycoses.
|
Tinea versicolor
Tinea nigra Black piedra White piedra |
|
|
What is the significance of cutaneous mycoses?
|
Includes dermatophytes and Candida.
Classic ring-shaped lesions; worldwide distribution; some develop into chronic, recurring infections |
|
|
What is the morphology of dermatophytes?
|
filamentous fungi = moulds
possess keratinolytic enzymes to allow parasitization of keratinized body tissues |
|
|
What three genera are dermatophytes?
|
Epidermophyton
Microsporum Trichophyton |
|
|
What are the two types of tinea capitis?
|
Endothrix infection
Ectothrix infection |
|
|
What are some etiologic agents for endothrix infections?
|
Trichophyton tonsurans, T. violaceum, T. schoeleinii
|
|
|
What causes "black dot"?
|
T. tonsurans endothrix infection
(causes the hair to break off at the surface) *most common isolate in US |
|
|
What causes favus?
|
T. schoenleinii
(will have scutula crusting with permanent loss of hair and scarring) |
|
|
What are some etiologic agents for ectothrix infection?
|
Microsporum audouinii, M. canis, and T. mentagrophytes
|
|
|
What can cause epidemic tinea capitis?
|
M. audouinii
|
|
|
Which two causes of ectothrix infection are zoophilic?
|
M. canis (can cause localized outbreaks)
T. mentagrophytes |
|
|
What are some etiologic agents of tinea barbae and who is most likely to aquire this?
|
T. verrucosum and T. mentagrophytes
Both are ectothrix infections and can be contracted from cattle = often seen in farmers/ranchers |
|
|
What is kerion?
|
Suppurative folliculits - commonly seen in eyebrow.
Caused by Trichophyton spp. |
|
|
What are some agents of tinea corporis?
|
Infects smooth skin.
M. canis, T. rubrum, T. mentagrophytes |
|
|
What is tinea cruris and what are two common etiologic agents?
|
"jock-itch"
Epidermophyton floccosum (groin, perineal, perianal) T. rubrum (extends over buttocks and waist) |
|
|
What is the most common cause of tinea pedis?
|
"athlete's foot"
T. rubrum |
|
|
What else can cause athlete's foot?
|
T. mentagrophytes
|
|
|
What is the most common cause of tinea unguium?
|
T. mentagrophytes
*also known as onychomycosis |
|
|
What are some agents used to treat dermatophytic infections?
|
1. desenex, tinactin --> desquamatory
2. topical azoles (miconazole -OTC) 3. terbnafine = lamisil 4. Itraconazole (oral therapy for chronic tinea unguium) 5. Grisofulvin - oral, old |
|
|
How do you prevent dermatophytic infections?
|
Keep skin dry and clean
|
|
|
What specimens are collected for lab ID of dermatophytes?
|
hair, skin, nails
|
|
|
What should you use for direct microscopic examination of specimens?
|
KOH prep + lactophenol cotton blue (contrast dye)
|
|
|
What is the most commonly used media to culture dermatophytes?
|
Sabouraud dextrose agar with and wo cycloheximide and chloramphenicol
*incubate 25-30 C for up to 4 weeks |
|
|
What is dermatophyte test media?
|
Differential media for dermatophytes:
- dermatophytes turn media RED (alkaline by-products) - bacteria and other fungi turn media YELLOW |
|
|
What is used to identify dermatophytes?
|
Colony morphology
Microscopic morphology (macroconidia and microconidia) Biochemical tests |
|
|
Describe the microconidia and macroconidia in epidermophyton.
|
Abundant macro
NO micro |
|
|
Describe macro and micro conidia in microsporum.
|
Abundant macro
Few micro |
|
|
Describe macro and micro conidia in Trichophyton.
|
Few macro.
Abundant micro. |
|
|
What are the two clinical diseases seen in sporotrichosis?
|
Lymphocutaneous disease (most common)
Pulmonary or disseminated disease (rare) |
|
|
How is lymphocutaneous sporotrichosis aquired?
|
Traumatic implantation of soil fungus
often seen due to: rose thorn, splinter, or similar puncture wounds |
|
|
What is the clinical presentation of lymphocutaneous sporotrichosis?
|
Painless papules appear 1-3 weeks after inoculation and then secondary and tertiary lesions appear distally along lymph channels
*spreads through lymph |
|
|
How is pulmonary or disseminated sporotrichosis acquired?
|
Acquired via inhalation
This is a rare but serious form seen in immunocompromised |
|
|
What is the etiologic agent of sporotrichosis and what is special about it?
|
Sporothrix schenckii
*** DIMORPHIC *** |
|
|
Describe the tissue phase and mould phase of S. schenkii
|
@ 37: long, cigar-shaped yests (rarely seen)
@25: dematiaceous septate hyphae; delicate conidiophores with pear-shaped conidia in rosette clusters |
|
|
What are asteroid bodies?
|
Yeast form of sporothrix that is rarely seen but is diagnositc of sporotrichosis.
Yeasts surrounded by eosinophilic halo - represent deposition of Ag-Ab complexes |
|
|
What is treatment for sporotrichosis?
|
Lymphocutaneous = itraconazole
Pulm/disseminated = AmpB |
|
|
Describe the disease chromomycosis.
|
Localized, chronic infection of skin and subcutaneous tissue that forms painless, cauliflower-like lesions.
Acquired by traumatic implantation. |
|
|
What is the etiologic agent of chromonycosis?
|
Slow-growing dematiaceous fungi
Many genera: Fonsecaea, Cladosporium, Exophiala, Wangiella, Philaophora spp. --> all macroscopically look like black mould |
|
|
What are the three types of sporulation seen with agents of chromomycosis?
|
Cladosporium type
Acrotheca or rhinocladiella Phialophora |
|
|
Describe the sporulation types:
|
Cladosporium = branching conidiophores with chains of conidia
acrotheca/rhinocladiella = club-shaped conidiophores with elongated conidia Phialophora = vase-shaped conidiophore with small eliptical conidia at top |
|
|
What are sclerotic bodies?
|
Brown segmented hyphal forms seen in infected tissue (adapts to adverse environment)
*Important diagnostic feature! |
|
|
What is therapy for chromomycosis?
|
itraconazole
surgical excision for advanced lesions |
|
|
What are two forms of mycetomas?
|
Includes actinomycetoma and eumycetoma
|
|
|
How is mycetoma acquired?
|
Traumatic implantation from soil
|
|
|
What kind of lesions occur in mycetomas?
|
Lesions involve skin, subcutaneous, fascia, and bone.
Form granulomas and abscesses that drain by forming sinus tracts |
|
|
What is a useful diagnostic observation of sinus tracts?
|
"grains" may be seen in sinus tract drainage that represent compact microcolonies of pathogens
|
|
|
What are the etiologic agents of eumycetoma?
|
Pseudallescheria boydii (most imp)
Madurella mycetomatis Exophila jeanselmei |
|
|
What are the etiologic agents of actinomycetoma?
|
Nocardia spp.
Streptomyces spp. Acinomadura spp. |
|
|
Describe P. boydii microscipically?
|
"lollipop-like" oval conidia produced from laterally short conidiophores
|
|
|
What is the term phaeohyphomycosis used to describe?
|
heterogeneous array of fungal infections caused by various dematiaceous fungi found in the environment
|
|
|
What does phaeohyphomycosis look like in tissue?
|
Pigmented, irregular hyphal forms
|
|
|
What does the extent of phaeohyphomycosis infection depend on?
|
Can be superficial, subcutaneous or deeply invasive depending on the fungus and the immune status of the host.
|
|
|
How does subcutaneous phaeohyphomycosis present?
|
solitary cyst-like lesions
secondary to traumatic implantation of contaminated soil or wood splinters |
|
|
What are some common etiologic agents of phaeohyphomycosis?
|
Exophila, Wangiella, Bipolaris
|
|
|
What is the main treatment for phaeohyphomycosis?
|
Surgical excision.
Itraconazole can be effective in some cases. |
|
|
What is the significance of "miscellaneous dematiaceous moulds"?
|
Usually recovered in clinical specimens as contaminants; Can be pathogens in debilitated hosts (=opportunists)
|
|
|
What are some common genera in miscellaneous dematiaceous moulds?
|
Curvularia
Alternaria Epicoccum Nigrospora |
|
|
What is the morphology of Curvularia?
|
geniculate conidiophores with 4 celled conidia
|
|
|
What is the morphology of Alternaria?
|
Large, racquet-shaped conidia in chains with transverse septations
|
|
|
What is the morphology of Epicoccum?
|
Pear-shaped multiseptate conidia that darken with age
|
|
|
What is the morphology of Nigrospora?
|
Large, black, oblong conidia on short conidiophores
|
|
|
What is the etiologic agent of Tinea versicolor?
|
Malassezia spp.
M. globosa, M. furfur |
|
|
When is infection with M. furfur typically seen?
|
After sun exposure
|
|
|
What does Malassezia spp. appear like under microscope?
|
"spaghetti and meatballs"
|
|
|
What is the etiologic agent of Tinea nigra?
|
Hortaea werneckii
**generally seen on palms of hands |
|
|
What is the etiologic agent of black piedra?
|
Piedra hortae
|
|
|
What is the etiologic agent of white piedra?
|
Trichosporon spp.
|
