26 intro to mycoses Flashcards
What organism is a common cause of tinea pedis?
Trichophyton rubrum
T-Fâ dermatophytes can not survive one the skin cells are shed? How does human to human transmission of tine pedis occur?
- False- can survive in shed skin cells for a long time
2. Fomites
What dermatophyte organism is a common cause of Tinea unguium?
Trichophyton rubrum
What 2 dermatophytes cause 80-90% of Tinea barbea ?
T. rubrum and T. mentagrophytes
The favus variant of Tinea capitis that causes scutula formation (yellow crusts composed of hyphae, neutrophils, and epidermal cells), can coalesce to cover much of the scalp is cause by what dermatophyte?
Trichophyton schoenleinii
What is involved in scutula formation?
yellow crusts composed of hyphae, neutrophils, and epidermal cells
What clinical ways do we diagnose dermatophytosis?
appearance and Woodâs lamp (UV365 nm)
[diagnosis usually stops at this]
What laboratory tests help us diagnose dermatophytosis?
- Direct microscopic examination (KOH)
- Culture : selective media
- Physiologic tests [hair perforation test, special a.a. and bit. requirements, Urea hydrolysis, growth on BCP-milk solids-glucose medium, Growth on polished rice grains, temp tolerance]
For rough walled macroconidia how do we distinguish types?
of cells
What is the dermatophytosis treatment if its localized?
topical antifungals
What is the dermatophytosis treatment for nail infection, extensive cutaneous involvement, T. capitis/barbae?
Oral therapy
What adjunctive therapies might be useful for T. barbae?
warm compresses, selenium sulfide
What are the 4 common characteristics of subcutaneous mycoses?
- trauma or implantation at site
- occur on body parts prone to trauma
- Etiologic agents usually found in soil/veg
- Difficult to treat
What are the 4 most common subcutaneous mycoses?
- sporotrichosis
- chromoblastomycosis
- phaeohyphomycosis
- Eumycotic mycetoma
What is lobomycosis= amazonian blastomycosis associated with?
Dolphins- Locazia loboi
What kind of infections does sporotrichosis cause?
Chronic infection involving cutaneous, subQ, and lymphatic tissue
What mainly causes lymphocutaneous sporotrichosis lesions? What is a general characteristic about it?
- Sporothrix schenkii
2. thermally dimorphic fungus found in soil
Who is sporotrichosis frequently found in?
Gardeners
In sporotrichosis skin lesions follows minor trauma, what are the steps of progressing problems?
noduleâ> ulcerâ> necrotic ulcerâ> then maybe subQ infectionâ> lymphatic channelsâ> lymph node involvement [systemic dissemination to bones, joints, meninges]
What samples do we need to test sporotrichosis?
aspiration fluid, pus, tissue biopsy
With sporotrichosis, what microscopy techniques do we use for diagnosis?
- Direct microscopic examination (KOH)
- Histopathological examination
[Yeast cells in tissue]
How many days does sporotrichosis diagnosis? What color does it turn?
- 3-5 days
2. brown/black
The sporothrix schenkii gram stain looks like what?
round to cigar shaped yeast form (darker than other tissue)
What temperature does sporothrix schenkii grow at? What are some basic characteristics of it?
- 25 C.
2. mycelial formâ>septate hyphae, rosette-like clusters of conidia
What is the treatment of sporotrichosis in a lymphocutaneous infection? disseminated infection?
- Itraconazole and heat
2. Amphotericin B +/- itraconazole
When do we often see chromoblastomycosis and phaeohyphomycosis?
Post-traum chronic infection of SubQ tissue, due to dematiaceous fungi
What does chromoblastomycosis infection look like?
papulesâ>warty nodulesâ> verrucous cauliflower on lower extremeties
Where is chromoblastomycosis most likely to be seen?
barefoot populations in tropical areas
What are fonsecaea, phialophora, and cladophialophora associated with commonly?
chromoblastomycosis
What is the tissue form of chromoblastomycosis infections?
sclerotic body
Are chromoblastomycosis often associated with systemic infection?
No
How do we diagnose chromoblastomycosis?
- Direct microscopic examination (KOH)- sclerotic body or medlar body seen.
- Culture- sabouraud dextrose agar 4-6 weeks
What specific organism of phaeohyphomycosis causes brain lesions?
Cladophialophora
What is the most common physical feature of phaeohyphomycosis? what is the tissue morphology?
- Phaeohyphomycotic cyst
2. mycelial (pigmented septate)
The phaeohyphomycosis infection can be caused by : Exophiala, Phialophora, Wangiella, Bipolaris, Exserohilum, Cladophialophora, Phaeoannellomyces, Aureobasidium, Cladosporium, Curvularia, and Alternaria (over 70 species in 39 genera).
HOW DO WE DIAGNOSE?
Histopathology and culture (skin scrap or biopsy the site)
Remember, tissue form is pigmented septate hyphae
What type of infection is characterized by post trauma chronic of Sub Q and can extend to fascia, muscle and bone? where is it often found
Mycetoma-(maduromycosis, madura foot)
-common in tropical climatesâbare foot
What are the two types of causative agents of mycetoma?
- Fungi (Madurella mycetomatis, Pseudallescheria boydii, Acremonium spp, Exophiala jeanselmei, Leptosphaeria spp, Aspergillus spp., Fusarium, Curvularia
) - Actinomycetes (BACTERIA!- actinomyces, nocardia, streptomyces)
What is a finding of eumycetoma?
abcess formation- draining sinuses containing granules, deformities, on lower extremities and hands
What about diagnosing eumycetoma?
nonspecific clinical, identifying fungus is difficult, characteristics of the granules and culture growth helps.
How do we treat chromoblastomycosis, phaeohyphomycosis, and eumycetoma?
surgical excision
antifungals (newer azoles and combinations)
what are the 3 simple clinical distinctions for fungi?
1) yeasts
2) moulds
3) dimorphic fungi
T/F we share a lot of the same properties as fungi?
True because we are so close on the evolutionary tree
Which organism is unicellular, round/oval, and reproduce by budding?
Yeasts
Which organisms are multicellular, reproduce by forming aerial hyphae with condida, and have both septate and non septate hyphae?
Moulds
What does it mean to be a dimorphic fungi?
you can exist as a mold or a yeast depending on growth conditions
what is a propagule?
a unit that can give rise to another organism
what is a conidia?
propagules formed asexually by breaking off of cells/branches.
What is arthrocondida?
conidia released by fragmentation of hyphae
what is Dematiaceous?
a fungus having brown or black melanotic pigment in the cell wall.
For our purposes, what is the only fungi with a polysaccharide capsule?
Cryptococcus neoformans
What makes up chitin?
NAG monomers
what is fungal cholesterol? where is it found?
Ergosterol=fungal cholesterol
Found in the cell membrane
T/F Fungi have membrane bound nuclei?
True, recall they are eukaryotes.
Why would you add KOH to a prep slide when looking for fungi?
Because it dissolves everything but the fungi because its cell wall protects its breakdown.
What stain is used to detect fungi in tissues?
Methenamine silver stain.
T/F In general, fungal organisms stain Gram positive and are acid fast?
False, they do stain gram +, but they are not acid fast.
Which stain binds chitin of fungi and turns it white?
Calcoflour white
what is aflatoxicosis?
A very potent toxin and teratogen released from some fungi
which layer of the dermis/epidermis is infected by fungi?
Any layer can be infected
3 superficial mycoses common features?
1) primarily a cosmetic problem
2) Little or no host Reaction
3) Easily diagnosis and treatment
What is the Malassezia furfur complex?
A group of 12 species of fungi that cause human to human transmission. Ex: tinea versicolor
What is another name for tinea versicolor?
Pityriasis
What 2 clinical features do you usually see with Tinea versicolor?
1) hyper/hypo pigmented areas on trunk or proximal limbs
2) light/dark spots usually do not itch.
what layer of the skin does tinea versicolor (pityriases) affect?
Its a chronic infection of the stratum corneum
How is tinea versicolor spread?
Human to human through the keratinous material of skin
why wont tinea versicolor grow on normal media?
it requires a lipid source to grow (olive oil)
If you see a slide with a yeast like growth and hyphal fragments that look like sticks and balls, what type of fungi should you think of?
Tinea versicolor (pityriasis)
What is the difference between Hortae, Exophiala, and cladosporium?
They are all the same thing. They are all fungi genus that cause tinea nigra. (Ex. Hortae werneckii)
what disease is characterized by browning maculae on the palms and soles and rarely other areas?
Tinea nigra caused by Hortae werneckii. These can look like a superficial melanoma.
What does tinea nigra look like under the micorscope?
Darkly pigmented
branched septate hyphae
elongated budding cells.
Macroscopically, what do the cultures of tinea nigra look like?
Black colonies
