What is a DTM fungal culture?
Dermatophyte Test Medium Fungal Cultures. Dermatophyte test medium (DTM) fungal cultures are used to isolate and identify dermatophyte organisms. DTM is made with special ingredients that inhibit bacterial growth and turn red when dermatophytes grow.
How do you culture a ringworm?
In animals, one of the best ways to collect a sample for culture is to comb over all the fur and skin with a new toothbrush, and then try to grow dermatophytes from the toothbrush. This allows the fur from all over the animal to tested, rather than just one little clump of fur plucked from one area.
What does a positive ringworm culture look like?
In order for a culture to be positive for ringworm, red medium color must appear first, or appear at the same time as a colony. If a colony appears first, it is likely not ringworm. Remember also that all culture media will turn red if left sitting on the shelf long enough.
What is a PCR test for ringworm?
When the history and clinical signs are compatible, a positive PCR test can confirm infection. The Ringworm (Dermatophyte) RealPCR Panel can also be used to screen exposed animals from the same household as an infected animal. If PCR negative in an exposed animal without lesions, dermatophytosis can be ruled out.
What does a positive DTM culture look like?
Dermatophytes grown on DTM are generally lightly pigmented (white, buff, tan or cinnamon-colored), whereas common saprophytes are often darkly pigmented. The colony surfaces of the dermatophytes of veterinary importance are often described as powdery, granular or cottony.
How long does ringworm culture take?
A positive culture can sometimes be confirmed within a couple of days, but in some cases, the fungal spores may be slow to grow, and culture results can take up to three weeks.
How do you perform a DTM test?
How do I do it?
- Use a scalpel with water to scrape and hemostats to pluck; take hairs and scale from the edge of a lesion (preferably the ones fluorescing under the Wood’s light)
- Impress hairs and scale gently on DTM; do not screw the lid tight.
- Incubate the agar at 20-25°C (a warm space with moisture is better)
How do you read a DTM?
In addition to observing for a red color change, the interpretation of DTM growth should include an assessment of gross and microscopic colony morphology. Dermatophytes grown on DTM are generally lightly pigmented (white, buff, tan or cinnamon-colored), whereas common saprophytes are often darkly pigmented.
How long does it take to grow a ringworm culture?
A positive culture can sometimes be confirmed within a couple of days, but in some cases the fungal spores may be slow to grow, and culture results can take up to four weeks.
How accurate are ringworm cultures?
PCR correctly identified all culture-positive cats and 92/104 culture negative cats; there were 12 false-positive PCR results. The sensitivity and specificity of PCR were 100% (95% confidence interval [CI] 87.7-100) and 88.5% (95% CI 80.7-93.9), respectively.
How can you tell if you have ringworm under a microscope?
To be certain of a diagnosis of ringworm, it is imperative to microscopically examine and positively identify the fungus….Identification
- Place a drop of lactophenol blue stain on a slide.
- Dab the sticky side of a piece of tape on the suspect colony.
- Place the tape over the drop of stain and examine under the microscope.