**Core Concept**
Dermatophytes are a type of fungi that infect the skin, hair, and nails, causing a range of skin conditions known as dermatophytoses. These fungi thrive in warm, moist environments, and their infection is facilitated by factors such as humidity, friction, and compromised skin integrity.

**Why the Correct Answer is Right**
Dermatophytes infect the keratin-containing tissues of the skin, hair, and nails. They secrete keratinases, enzymes that break down keratin, allowing the fungi to penetrate and colonize the infected tissue. The most common dermatophytes are Trichophyton, Microsporum, and Epidermophyton species, which cause a range of conditions including ringworm, athlete's foot, and onychomycosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the type of infection caused by dermatophytes.
**Option B:** This option is incorrect because it does not accurately describe the mechanism of dermatophyte infection.
**Option C:** This option is incorrect because it does not provide a relevant or accurate description of the effects of dermatophytes.

**Clinical Pearl / High-Yield Fact**
Dermatophytes can be treated with topical or systemic antifungal agents, but it is essential to note that recurrence is common if the underlying cause of the infection (e.g., poor hygiene, warm environment) is not addressed.

**Correct Answer: D. Keratin-containing tissues.**