Bacteriology exam2
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- What 2 species will form a germ tube? How may they be differentiated?
-
Candida albicans
C. stellatoidea
C. albicans is sucrose positive, while C. stellatoidea is sucrose(-) - This differentiates pseudohyphae from true hyphae?
- constrictions between adjacent cells
- The most common example of dermatophytosis is -
- Ringworm
- What 3 genera comprise the deratophytes?
- Microsporum, Trichophyton, and Epidermiphyton
- In a lesion formed by ringworm would it be more beneficial to take a sample from the edge or from the center of the lesion?
- from the center
- This yeast is commonly associated with otitis externa-
- Malassezia pachydermatis
- The key membrane lipid in fungi is -
- ergosterol
- T/F Griseofulvin is active against a wide range of fungi
- False - Griseofulvin is only effective agains dermatophytes
- Where is griseofulvin concentrated?
- newli formed cells of skin, nails, and hair
- Griseofulvin prevents mitosis by interfereing with what?
- Mitotic spindle formation
- T/F Resistance to Griseofulvin is uncommon
- True
-
Amphotericin B has ___________ action.
A) Fungistatic
B) Fungicidal - Fungistatic
-
Amphotericin B toxicity is likely to be seen in
A) Liver
B) Heart
C) Lungs
D) Kidney - D) Kidney - nephrotoxicity
- Explain the 2 mechanisms of action of 5-FC (Flucytosine)
-
1) Converted to 5-fluorouracil which replaces RNA in the cell
2) 5-FU converted to 5-fluorodeoxyuridine monophosphate which inhibitds thymidine producion neccesary for DNA synthesis. - Since 5-FU is the active form why is 5-FC (Fluocytosine) used.
- 5-FU is not taken up by fungi and is toxic to mammalian cells
- Why are 5-FC and Amphotericin-B often used in combination?
- Less Amphotericin is neccesary and amphotericin makes the fungal cell wall more permeable to 5-FC