Medical Fun Facts Podcast

MFF0018: Dermatophilus congolensis

Regular listeners of Medical Fun Facts may have noticed I’m now trying to drop a show on Mondays and Thursdays. Usually in the evenings, eastern Australian time. I’ve also started doing shows alphabetically.

So today’s show begins with the letter D. I was thinking of Dientamœba fragilis, but I thought that would be too soon after Blastocystis hominis. So for today’s show, I’ve selected Dermatophilus congolensis. Now, doesn’t that sound exotic?

My first recollection of Dermatophilus congolensis was in about 1984 when I purchased a copy of the third edition of the Manual of Clinical Microbiology from the American Society for Microbiology. I was in the second year of medical school and I was putting myself through by working in a medical testing laboratory. I’d already worked out I wanted microbiology in my future after loving it in high school.

I recall one of the first things that struck my eye as I was leafing through the pages was a small section on Dermatophilus congolensis.

Dermatophilus congolensis is Gram-positive and causes Dermatophilosis in animals and humans. Dermatophilosis is a dermatologic condition that manifests as crusty scabs that contain the bacterium. Please note, it is not mycotic dermatitis.

Dermatophilus congolensis is a facultative anaerobic actinomycete. It exists in two forms, viz., filamentous hyphæ and motile zoöspores. The hyphae are branching filaments which fragment into packets of spherical cells. These spheres mature into flagellated ovoid zoöspores. The coolest thing about this bacterium is that it forms motile zoöspores. It can almost look like a fungus because it has branching hyphæ and it can change appearance and break down into these mobile ovoid zoöspores. Notice how I say zoöspores. It’s like a zoölogical garden. Sure you can visit a zoo but the formal name is a zoölogical garden.

Frequently infected animals include cattle, horses, sheep and goats. Humans get infected when handling infected animals. Dermatophilosis is known by many common names like cutaneous streptothrichosis (on cattle, goats, and horses), “rain-scald” (on horses), and “lumpy wool” (on sheep).

The natural habitat of Dermatophilus congolensis is not clear. It probably lives in the soil. It really only gets isolated from the living layers of the epidermis. The primary reservoir is thought to be asymptomatic chronically infected animals.

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