Dermatophytes are cutaneous keratophilic fungi. They cause concentric skin lesions. As a sample, usually skin scrapings are collected.
When viewed under the KOH mount, they appear transparent but when cultured, they show varied pigmentation. In fact, there is different pigmentation both on the obverse and reverse of the culture media (SDA), which makes pigmentation a differentiating and identification feature. These colors vary from species to species from red to violet.
So here are my questions
- Is the pigment secreted out in the medium or retained in the hyphae? How are the fungi transparent on a KOH mount.
- Why is there a different pigmentation on the obverse and reverse?
- Why is there no colour in the skin lesions? There is just erythema if I'm not mistaken.