Stains and ID methods Flashcards
List the 6 methods of direct examination of fungi
- Saline wet mount
- Lactophenol cotton blue wet mount
- Potassium hydroxide
- Gram stain
- India ink
- Calcofluor white stain
What is the purpose of lactophenol cotton blue?
It colors the fungal structures blue to allow for easier preliminary ID
What is the purpose of KOH in the direct examination of fungi?
Useful for detecting dermatophytes, tissue, and respiratory specimens. the KOH dissolves keratinaceous material so it doesn’t interfere with the examination, so it’s appropriate for vaginal specimens
What is the purpose of India ink prep? Is it a stain?
It is used to visualize capsules. The ink does not color the capsules, so you see a clear capsules in a dark background. It is NOT considered a stain
What is the purpose of a Calcofluor white stain?
It greatly enhances the visibility of fungi by binding to the cell walls (chitin), causing the fungi to fluoresce blue-white
Directly from Mycology quiz 3
List 2 types of nonselective media
- Sabouraud Brain Heart Infusion Agar (SABHI)
- Brain Heart Infusion Agar with Blood (BHIB)
List 4 types of selective media
- Inhibitory Mold Agar (IMA)
- Brain Heart Infusion Agar with Blood and antibiotics
- Mycosel
- Dermatophyte Test Medium (DTM)
What is the purpose of BHI?
Primary recovery of fungi. Rich media for bacteria, yeast, and pathogenic fungi
What is the purpose of BHIB?
Primary recovery of fungi, including systemic dimorphic fungi. Rich medium for isolation of pathogenic fungi (system/dimorphic)
What is the purpose of BHIB + Abx?
Abx = antibiotics
Primary recovery of pathogenic fungi and excludes both dermatophytes and bacteria
What is the purpose of Chromogenic agar
Color changes depending on yeast ID. Allows to distinguish between different Candida species and Candida albicans
What is the purpose of DTM?
To select for dermatophytes only
What is the purpose of IMA?
Recovers pathogenic fungi. Contains cyclohexamide (inhibits saprophytes) and chloramphenicol (inhibits bacteria
https://www.thermofisher.com/order/catalog/product/R08410
Mycology Quiz 3, Question #6 and the Mycology intro slides are the resources for this answer
What is the purpose of Mycosel agar?
Primary recovery of dermatophytes. Some other fungi may grow. Inhibits bacteria and saprophytic fungi
What is the purpose of Sabouraud dextrose with brain-heart infusion agar
(SABHI)?
Isolates and enhances growth of all fungi
What are the general culture conditions for fungi?
- 30°C
- Humid
- 3 to 4 week incubation time
- BSC
- Sealant
- Culture tubes vs plates
Which macroscopic morphological characteristics do you examine on a plate?
- Color
- Texture
- Surface and Reverse
List the 5 fungal differential agars
- Potato dextrose agar (PDA)
- Bird seed (niger seed) and caffeic acid agars
- Cornmeal agar with Tween 80
- Yeast ChromAgar
- Agars with rice, casein, and other nutrients
Tween 80 is a detergent
What is the purpose of Bird seed and caffeic acid agar?
To select for organisms that produce the enzyme phenoloxidase, which oxidizes caffeic acid in the medium to melanin. This produces a red-brown pigmentation
Resource: MediaLabs
Cryptococcus neoformans grows on this plate
What is the purpose of Potato Dextrose Agar (PDA)?
Potato Dextrose Agar (PDA) is used for the cultivation of fungi. It is a general purpose medium for yeasts and molds that can be supplemented with acid or antibiotics to inhibit bacterial growth. It is recommended for plate count methods for foods, dairy products and testing cosmetics. PDA can be used for growing clinically significant yeast and molds. The nutritionally rich base (potato infusion) encourages mold sporulation and pigment production in some dermatophytes
[https://microbiologyinfo.com/potato-dextrose-agar-pda-principle-uses-co
What is the purpose of Cornmeal agar with Tween 80?
Corn Meal Agar is primarily used to
elicit chlamydospore production by Candida
albicans
https://www.dalynn.com/dyn/ck_assets/files/tech/TC81.pdf
Chlamydospore: enlarged, thick-walled vegetative cells with varied forms and condensed cytoplasm that form within hyphae or at hyphal tips
What is the purpose of ChromAgar?
CHROMagar Candida (CAC) is a selective medium for the isolation of fungi that simultaneously provides direct differentiation and identification of several Candida species (9). The yeasts produce enzymes that react with chromogenic substrates in the CAC medium, producing colonies of different colors.
C. albicans is green
