**Question:** The medium of choice culturing yeast form of dimorphic fungi is -

A. Sabouraud Dextrose Agar (SDA)
B. Blood Agar
C. Chocolate Agar
D. MacConkey Agar

**Correct Answer:** A. Sabouraud Dextrose Agar (SDA)

**Core Concept:** Dimorphic fungi are a group of fungi that can switch between yeast and mold forms. The yeast form is the more common form and is responsible for causing infections.

**Why the Correct Answer is Right:** Sabouraud Dextrose Agar (SDA) is the preferred medium for culturing dimorphic fungi due to its composition and properties. SDA contains dextrose, which supports the growth of yeast cells, and chloramphenicol, an antibiotic that inhibits the growth of bacteria and allows yeast cells to grow uninhibited.

**Why Each Wrong Option is Incorrect:**

B. Blood Agar: Blood Agar is typically used for culturing bacteria, not yeast cells of dimorphic fungi. The presence of blood attracts bacteria and may hinder the growth of yeast cells.

C. Chocolate Agar: Chocolate Agar is primarily used for culturing anaerobic bacteria. It lacks the specific components required for yeast cells of dimorphic fungi to grow.

D. MacConkey Agar: MacConkey Agar is primarily used for culturing gram-negative bacilli and is not optimized for yeast cells of dimorphic fungi.

**Clinical Pearl:** Identifying dimorphic fungi is crucial in clinical practice as they can cause infections in humans, especially in immunocompromised patients. Prompt diagnosis and appropriate antifungal therapy can improve patient outcomes.

**Explanation:**

The yeast form of dimorphic fungi is essential to identify for proper diagnosis and treatment of infections caused by these fungi. By culturing on SDA, the yeast cells can grow and be isolated, allowing for further identification and antifungal susceptibility testing.

**Why the Correct Answer is Right:**

Sabouraud Dextrose Agar (SDA) is the optimal medium for culturing yeast cells of dimorphic fungi due to its composition and properties. The presence of dextrose as the primary carbon source supports the growth of yeast cells, and the addition of chloramphenicol (an antibiotic) inhibits bacterial growth, allowing the yeast cells to grow uninhibited.

**Why Each Wrong Option is Incorrect:**

Blood Agar is typically used for culturing anaerobic bacteria, not yeast cells of dimorphic fungi. The presence of blood cells in the medium may hinder the growth of yeast cells.

Chocolate Agar is primarily designed for culturing anaerobic bacteria and lacks the specific components required for yeast cells of dimorphic fungi to grow.

MacConkey Agar is designed for culturing gram-negative bacilli, not yeast cells of dimorphic fungi. The medium lacks the specific components required for yeast cells to grow.