Dermatophytes Review Questions Flashcards
What is a dermatophyte?
A dermatophyte is a pathogenic fungus (parasite) that invades hair, nails, and superficial layers of the skin. These fungi cause pruritus, and crusty debris. Lesions are usually characterized by spreading areas of pruritus and accumulation of crusty debris. Lesions can be single or multifocal, and hair loss is variable.
Where can it be found on an animal?
Dermatophytes can be found on the hair, nails, and superficial layers of the skin.
What is DTM and what dermatophyte is it specific for (give both names)?
DTM is Dermatophyte Test Medium. It is a test medium that contains a phenol red indicator to assist in the identification of ringworm, or Microsporum canis.
What would a positive DTM culture look like?
In a positive DTM culture, the medium will turn red. Colonies of growth will be white or light shades of apricot, yellow, or cream to tan in color.
What would a contaminant look like?
A contaminant colony would be brown or black in color. No media color change.
What stain is used for microscopic evaluation of the organism?
Lactophenol Blue is used to stain samples of the colonies from the DTM, and then they are evaluated under the microscope.
What is the Wood’s Lamp and what is it used for?
The Wood’s Lamp is an ultraviolet lamp used to check the animal for Microsporum canis. About 60% of positive cases of Microsporum canis will fluoresce an apple green under a Wood’s Lamp in a dark room.
What supplies are needed for a skin culture and why would it be performed?
In order to do a skin culture you need: cotton, culture media, sterile 22-gauge needle or scalpel blade (for bacterial culture), scalpel blade or hemostatic forceps (for fungal culture), and 70% alcohol (for bacterial culture).
You would perform a skin culture to identify bacterial and fungal pathogens of the skin, and to determine the antibiotic sensitivity of bacterial skin pathogens.
What supplies are needed for a skin scraping and why would it be performed?
In order to do a skin scraping you need: a scalpel blade, glass slides, and mineral oil or potassium hydroxide.
You would perform a skin scraping to detect the presence of microscopic skin parasites.
What is the cellophane tape preparation and what parasite is it used for?
The cellophane tape preparation is the use of cellophane tape to collect material from the surface of the skin and hair coat. It checks for the presence of certain skin parasites, including flea larvae, lice and mites.
- Skin biopsies are performed using what tool?
A skin biopsy punch is used to perform a skin biopsy.
What stain is used for a positive DTM culture?
- In the DTM media itself, phenol red indicator is used. This will turn red if the DTM is positive.
- After getting a positive result with a DTM culture, you can take prepare a slide with a sample from one of the colonies on the DTM and stain it with Lactophenol Blue. This slide can be examined under the microscope to confirm the positive results from the DTM.
