**Core Concept**
Naegleria fowleri is a free-living amoeba that causes primary amebic meningoencephalitis (PAM), a rare but often fatal disease. To isolate and culture this pathogen, a selective medium is required that supports its growth while inhibiting the growth of other microorganisms.

**Why the Correct Answer is Right**
The correct answer is **C. Non-nutrient agar with Escherichia coli (E. coli) as a nutrient source**. Naegleria fowleri requires a nutrient-rich environment to grow, and the presence of E. coli on non-nutrient agar provides the necessary nutrients for its growth. The amoeba is attracted to the E. coli and feeds on it, allowing it to multiply and form cysts or trophozoites, which can then be identified microscopically.

**Why Each Wrong Option is Incorrect**
**Option A:** Blood agar is a general-purpose medium that supports the growth of a wide range of bacteria and fungi, but it does not selectively support the growth of Naegleria fowleri.

**Option B:** Sabouraud dextrose agar is a selective medium for fungi, particularly dermatophytes, and is not suitable for culturing Naegleria fowleri.

**Option D:** Loeffler's serum slope is a medium used to culture Corynebacterium diphtheriae, and it does not support the growth of Naegleria fowleri.

**Clinical Pearl / High-Yield Fact**
Naegleria fowleri can infect humans through contaminated water, particularly in warm, freshwater environments such as lakes, rivers, and hot springs. The amoeba enters the body through the nasal passages and migrates to the brain, where it causes inflammation and damage to brain tissue.

**Correct Answer: C. Non-nutrient agar with Escherichia coli (E. coli) as a nutrient source**