A Micrscopic Look at Ringworm

Ringworm

Ringworm is a dermatophyte, meaning a fungus that feeds on keratin: skin, hair, nails, etc. More specifically, ringworm feeds on the outer layer of skin and hair follicles and this causes the hair to become brittle and break.

Diagnosis can be made several ways. Visually, ringworm often causes balding and ring shaped lesions on the skin. It doesn’t always cause these affects and infections can be confused with other dermatophytes and skin conditions. Some species will fluoresce green or blue under a woods lamp, but again, not guaranteed. Another diagnostic method is culturing skin and hair from the affected area. It is cultured in dextrose agar with phenol red and kept at room temperature for 7-10 days. A positive culture will turn the agar red. Ringworm can be very contagious and could spread to others in the time it takes for a positive culture. Ringworm can also be diagnosed by looking at a sample under a light microscope. This is the fastest, most reliable method. Some species of ringworm are species specific, whereas others are zoonotic. The three most common are : Trichophyton mentogrophytes, Microsporum canis, Microsporum gypseum and these are all zoonotic.

· Trichophyton is the most common in humans.

· Microsporum Canis is the most common in cats and dogs.

Species are identified by the shape and number of cells in the macroconidium; a large spore that is produced through vegetative reproduction. They grow on specialized hyphae until mature.

KOH and tape
KOH and tape

Methods and Procedure

All slides were prepared with a coverslip and sealed with clear nail polish. The accepted method for collecting spores is to take a piece of cellophane tape and lightly graze it over the culture. The tape is then placed a slide with any stain that will be used. I placed the tape on the coverslip so I wouldn’t have to try to focus through the tape. I wanted to compare this with taking whole sections. I obtained sections by scraping cultures with a needle. I then scrambled the needle in a drop of stain or milipore water and applied the coverslip. I also wanted to experiment with different stains. I compared Lactophenol cotton blue, which is a stain used with light microscopy

· Calcoflour

· Calcoflour and KOH

· KOH is used with cotton blue to help the stain adhere better to the membranes

I also compared these to spores without stain and auto-fluorescence only. I first looked at a slide prepared with a tape sample with lactophenol cotton blue. This did not fluoresce at all so I did not go any further with it, such as adding KOH. This is similar to what spores would look like under a light microscope, only with lactophenol, it would appear blue.

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Anonymous 3 years ago

I am into fungi and I have a microscope and I happen to have come down with ringworm. Exciting, I know. But I can't seem to locate any spores on tape from my skin. How are spores collected for culture?

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