Which medium is selective for dermatophytes and commonly used for screening purposes?

• A. Dermatophyte Test Medium
• B. Mycosel Agar
• C. SABHI Agar
• D. Corn Meal Agar

Answer: (A)

Dermatophyte Test Medium is designed to screen for dermatophytes by combining selective agents that suppress contaminants with a pH indicator that reveals when dermatophytes grow. The medium includes antibiotics and cycloheximide to reduce bacteria and non-dermatophyte fungi, making it selective for dermatophytes. As dermatophytes metabolize keratin, they alkalinize the medium, causing the phenol red indicator to turn red. That color change provides a quick, visual presumptive result, typically within a few days, which is why this medium is widely used for screening. If there’s no color change after about a week, dermatophyte growth is unlikely, though confirmation with additional tests is still advised. Other media have different uses—Mycosel Agar is often used for isolation by suppressing contaminants, while Corn Meal Agar is more about studying morphology, and SABHI Agar serves other diagnostic roles—so for rapid screening, Dermatophyte Test Medium is the most practical choice.