Mycology Flashcards
a) define mycoses
b) What are the four principle types of mycoses?
a) mycoses: fungal infections of body
b) • Superficial and cutaneous mycoses: Keratin (hair, skin, nails) and mucous membranes
• Subcutaneous: Dermis, tiss, bone
• Systemic: Internal organs (esp lungs)
• Opportunistic: infections in immunocompromised (young, elderly & sick) => result in above mycoses
What general growth conditions do fungi prefer?
- moist (incubate in dark chambers)
- low pH
- High [glucose]
- 20-28ºC
List two disadvantages or problems associated with antifungal drug therapy? How are patients monitored?
- treatment is usually long term
- toxicity (bc dealing w/ eukaryotic organisms- same as us)=> must have regular FBC (blood), LFT (liver) & RFT (renal)
Why are samples of skin, hair or nails treated with 10-20% KOH? (3)
- Clears keratin
- Separate cells
- Helps detection and examination
a) What is the common component of hair, skin and nails that the Dermatophyte fungi invade/require for growth? b) Which genera use which?
a) Keratin
b) - Trichophyton sp.: nails, skin, hair
- Epidermophyton sp. : nails, skin
- Microsporum sp.: skin, hair (M.canis: pets, animals)
What are coencytic hyphae?
Aseptate hyphae (continous hypahe contaning spores)
In a typical mould, what is the name of the segment of hyphae from which spores grow?
Septate (segmented hyphae containing spores)
In a mould that produces a spore sac (sporangium), what is the name of the segment of hyphae from which the sac grows?
Sporangiophore (-phore: “bearing”/ to bear)
Why do culture media for the isolation of fungi and yeast often contain a chemical agent such as Chloramphenicol or Cycloheximide?
Kills bact @ toxic [ ] = allow mould & yeast to grow
What group/type of people would be considered to be immunocompromised?
- Elderly
- young
- sick: immune disorders - AIDS or following chemo
Why are the lungs, the primary site of infection for many fungal diseases?
Spores are in the air & easily to inhale it
Which organism is primarily associated with fungal meningitis in the immunocompromised?*
Cryptococcus neoformans
Candida sp.
What test is characteristically positive for Candida albicans? How is the test performed and what denotes a positive result?
Germ tube test:
- incubate yeast colony in horse/human serum @ 37ºC for <2hrs (prolonged time hard to identify w/ other Candida sp)
- Pos: tube-like projection from yeast cell (true hyphae)
What colony feature (if present/seen) is characteristic of C.albicans?
BA: Starburst colonies (small filaments growing out of yeast colony) but not always see
Chromogenic media: green colony
What are the types of fungi?
- Moulds: multicellular filamentous colonies (fluffy)
- Yeasts & yeast-like fungi: single cells -> colonies
- Dimorphic fungi: can grow like moulds/filamentous (room) or yeast/colony (37ºC) depending on temp.
What is the difference between pseudohyphae and true hyphae?
True: parallel sides w/ no constrictions
Pseudo: sausage-like constrictions
a) Which one of the dimorphic fungi does not start as lung infection?
b) Usual treatment
c) what type of mycoses does all dimorphic fungi cause
a) Sporothrix schenckii
b) self-limiting (no treatment) depending on size of inoculum
c) Systemic infections, esp immunocompromised
How is the role of fungal spore different to bacterial spore?
Fungal spore: for fungal (a/sexual) reproduction
Bact. spore: survival of the bact. when conditions are unfavourable to live in, & can withstand harsh conditions => germinate once condition becomes favourable
Why is sputum collected early in the morning?
- easy to collect bc sputum build up overnight
- food can have yeast & spores (interfere)
What is the difference between aerial hyphae and vegetative mycelium (hyphae network)?
- Ariel: give rise to repro. spores on surface
- Vegetative: nutrient absorbing & H2O exchange under media/tissue
name 4-7 dermatophyte infections (ring worm & tinea) and state what superficial areas is affected
- Tinea capitis: skin & hair
- Tinea corporis: trunk, limbs & extremities
- Tinea cruris: groin & pubic area
- Tinea pedis: feet
- Tinea manuum: hands
- Tinea unguium: finger nails & toe nails
- Tinea barbae: beard
Lab features of Cryptococcus neoformans
- Large capsule (demo w/ India ink wet prep)
- Mucoid colonies
- Bird seed agar: brown
- Urea: pos
- Use latex agglutination to detect genus
- S to cyclohexamide
Colour of Candida albicans when grown on chromogenic media (@42-45ºC)
green
Distinduish b/w following asexual conidia/conidiospores
- Arthospores/arthoconidia
- Blastospores/blastoconidia
- Chlamydiospores/chlamydoconidia
- Microconidia vs. macroconidia (-spore)
- Sporangiospores
- Artho: spores within hyphael segments
- Blasto: budding yeast cells
- Chlamydio: thick walled resting spores
- Micro: little single-celled spore
- Macro: lrg multicellular spore
- Sporangio: spores held w/in a sack (sporangium)
