Cultivation of fungi, and microbiology diagnosis of fungal infections Flashcards Preview

Micro Semester 2 > Cultivation of fungi, and microbiology diagnosis of fungal infections > Flashcards

Flashcards in Cultivation of fungi, and microbiology diagnosis of fungal infections Deck (4)
Loading flashcards...
1
Q

What is the standard media for fungi?

A

Sabourad’s agar.

Beef broth-dextrose mixture.

Glucose - Carbon source
Peptone - Nitrogen source

Peptone provides nitrogen and creates a pH ~5.0.

The low pH inhibits most bacterial growth.

Growth can be slow, and 4 weeks is needed to prove a negative reseult.

2
Q

What are the other possible agars.

A

Chrome agar = differentiates species of candida by color.

Normal agar, fungi grow well on most agars

Blood agar 5-10% is good for dimorphic fungi.

Czapek’s solution
Used for Aspergillus and Penicillinum

Rice tween agar: for chlamydospores (candida albicans)

TTC: Tetrazolium chloride.

Penicillin, streptomycin are often added to inhibit bacterial growth.

Cycloheximide can be added to slow the growth rate of rapidly growing yeasts.

3
Q

Microbiological diagnosis of fungal infections

A

Scraping or or clinical samples stained with a wet mount in 10%-30% KOH.
KOH dissolves the skin cells but not the fungus with its cell wall.

PCR for fungal DNA in blood or sample is very good and sensitive.

Serology tests - generally insensitive, except for histoplasmosis and coccidioidomycoces.

Skin tests, for allergic bronchopulmonary apergillosis, Arthus test

4
Q

What stains can be used for fungi?

A

Gomori/Grocott silver stain is the best. Stains all fungi.

KOH and India ink.
India ink is a negative stain, staining the background black and the capsulated yeasts will still be light. -cryptococcus

PAS, stains yeasts and hyphi.

Mucicarmine red stains capsule - cryptococcus neoformans

Calcofluor white stain. Stains P carnii cell wall.

Giemsa stain can show intracellular
histoplasma capsulatum or intracystic P. carniii.

Gram stains
H&E stains also both work