Mycology Flashcards
What type of immune response does the chitin wall of fungi induce in their hosts?
A chronic granulomatous inflammatory response (where greater than 50% of cells are macrophages) because chitin is very resistant to degradation
What compound in the cytoplasmic membrane of fungi do anti-fungal drugs target?
Ergosterol
What are the 3 pathogenic mechanisms of fungi?
- Mycosis (invasion of host tissue)
- Hypersensitivity (aerolized fungi via spores/conidia released in the air)
- Mycotoxins (fungal toxins ingested, absorbed, etc. by host)
What are the 5 required conditions for mycosis to occur?
- Presence of virulence factors (e.g., capsule)
- Appropriate tissues are affected (e.g., dermatophytes and keratin-rich tissues)
- Appropriate immune status of host (e.g., breed susceptibility like german shepherds)
- Appropriate geographic location
- Appropriate environment (e.g., blastomyces have increased spore production in wet (rainy) environments)
How does a Dermatophyte Test Medium (DTM) identify fungal infection?
The yellow agar contains a pH indicator that turns red when present dermatophytes eat the protein in the agar and grow (low -> high pH)
What sort of sample do you collect for a dermatophyte culture, and how do you transport it?
Dermatophytes eat keratin: collect nails/skin/hair and transport in a sterile container @ RT
What sample is preferred for a fungal culture?
fresh tissue and/or fluid
What diagnostic test is best for superficial skin samples?
A direct exam: wet mount cytology using lactophenol cotton blue or new methylene blue mounting fluid, which allow for better visualization of fungal morphology
What color do fungal walls appear in a Gamori’s Methenamine Silver (GMS) stain on histopathology?
Black (by taking up the silver in the stain)
What samples do you submit for antibody and antigen detection diagnostic tests?
Antibody: blood serum
Antigen: blood serum or urine
What kind of fungus is yeast?
unicellular form of fungus that reproduces via budding
What growth form of fungi are psuedohyphae?
chains of yeast that look like hyphae
What growth form of fungi hyphae (mold)?
The branching, filamentous structure of a fungus (and collectively are a called mycelium)
Describe mycelium, the structure of hyphae that gives mold its distinctive “fuzzy” appearance, and how it arises.
Mycelium = branching, thread-like mass of vegetative hyphae
Hyphae give rise to “fruiting bodies”, structures that play a role in the dispersal of spores/conidia–> spread out and give “fuzzy” appearance
What are the pathogenic and non-pathogenic forms of dimorphic fungi, and what determines the form?
- Pathogenic = yeast (form in host tissues)
- Non-pathogenic = hyphae (form in environment)
forms are temperature-dependent
What type of hyphae is the image on the left? On the right?
Left: septae (walls b/w cells –> distinct cells)
Right: non-septae (lack walls –> non-distinct cells)
How do spores/conidia form new organisms?
By germination via a germ tube
What type of spore/conidia released by dermatophytes is observed in PATIENTS?
Arthrospores/Arthroconidia: seen as multiple small, round structures
What two forms of dermatophytic spores/conidia are observed in the LAB?
Macroconidia and Microconidia
