Dermatophytes are defined as what?

• A. The fungi that causes skin nail and hair infections
• B. A type of bacteria
• C. A virus
• D. An algae

Answer: (A)

Dermatophytes are fungi that invade keratinized tissues—skin, hair, and nails—causing dermatophytosis such as ringworm, athlete’s foot, and nail fungus. They’re not bacteria, viruses, or algae; those are different kinds of organisms. Dermatophytes use enzymes like keratinase to digest keratin, which is why they specifically affect these tissues. Common examples come from the genera Trichophyton, Microsporum, and Epidermophyton. Clinically, infections appear as itchy, scaly patches on skin or brittle, discolored nails. Diagnosis is usually by examining skin scrapings under a microscope after a potassium hydroxide prep or by fungal culture, and treatment ranges from topical antifungals for mild skin infections to systemic antifungals for nails or more extensive disease.