Question | Answer |
If the colony color is white, tan, pink, or salmon what might be growing? | Dematiaceous yeasts |
Why is Corn Meal-Tween 80 agar used? | Encourages development of chlamydospores; can see hyphae, pseudohyphae; clear media-can view under light microscope; specific organisms associated w/specific morphology |
What are the 4 main types of cornmeal agar morphology? | Hyphae, Pseudohyphae, Arthroconidia, Chlamydoconidia or blastoconidia |
What has pseudohyphae and blastoconidia only on cornmeal agar? | C. krusei, C. parapsilosis, C. kefyr, C. tropicalis |
What has blastoconidia only on cornmeal agar? | C. glabrata, C. neoformans |
What has arthroconidia on cornmeal agar? | T. beigelii |
What physiological tests are used to differentiate yeast? | Germ tube test, assimilation/fermentation, urea hydrolysis, temperature studies |
Order to follow for identifying yeast | Wet prep, Germ tube, If germ tube negative plate on CMT, Physiological/biochemical tests |
What is involved in germ tube test? | Serum, plasma, or commercially made broth; incubate for 2 hours; very time sensitive |
What yeast forms a "true" germ tube? | C. albicans |
What is a "true" germ tube? | No constriction at base where the tube attaches to the mother cell |
If a germ tube has a contricted base what yeast is indicated? | C. tropicalis |
Definition of fermentation | Carbohydrate use in absence of oxygen |
What does an assimilation test tell us? | What can be used as a sole carbon source, carbohydrate assimilation |
Two types of assimilation systems for identifying yeast | API 20C-strip test; Vitek-automated |
What does a urease test differentiate? | Cryptococcus from Rhodotorula |
What temperature does Cryptococcus spp. grow at? | Weakly at 35C, no growth at 42C |
What group has several spp. that grow well at 45C and higher? | Candida spp. |