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What is corn meal agar used for
to encourage development of chlamydospores (hyphae)
Place coverslip on agar and observe at 40x
On cornmeal agar, which candida are pseuohyphae and blastoconidia positive?
- C. krusei
- C. parapsilosis
- C. kefyr
- C. tropicalis
On cornmeal agar, which candida are blastoconidia ONLY
- C. glabrata
- ~C. neoformans
On cornmeal agar, which spp. has arthroconidia
What are the typical steps in the workup to identify C. albicans or other possible yeast.
- Start with:
- Wet prep &
- Germ tube - looking for filamentous outgrowth from blastoconidia
- If germ tube negative: proceed with
- CMT (cornmeal agar test) &
- Biochemical tests
Germ Tube Testing info
Not valid after 2 hours
Use serum or plasma or comercially made broths (which last longer)
Over and under incolulation is the biggest problem.
What is the principle of the germ tube
When grown in serum or plasma at 35C, some yeast have the abiltiy to form hyphae. This is an important characteristic in the identification of C. albicans.
What are the positive and negative controls for the germ tube
- Pos = C. albicans
- Neg = Cryptococcus spp.
Special temp requirements for
Cryptococcus spp &
Cryptococcus - weak growth at 35C and none at 42C
Candida - Grow well at 45C