## **Core Concept**
The question tests knowledge of sulfonamide antibiotics, specifically their spectrum of activity and clinical applications. Sulfonamides are a class of antimicrobials that inhibit folic acid synthesis in bacteria. The question focuses on a specific sulfonamide used topically for its activity against *Pseudomonas* in burn cases.

## **Why the Correct Answer is Right**
Mafenide acetate (also known as mafenide) is a sulfonamide antibiotic with a broad spectrum of activity, including against *Pseudomonas aeruginosa*. It is particularly noted for its use in burn creams for topical application to prevent infection in severe burns. Mafenide acetate can penetrate burn eschars effectively, making it suitable for this application. Its use helps in preventing infections that could complicate the healing process in burn patients.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Sulfadiazine is a sulfonamide used in combination with pyrimethamine for treating toxoplasmosis and in some topical preparations, but it is not specifically known for activity against *Pseudomonas* or for use in burn cases in the same way as mafenide acetate.
- **Option B:** Sulfamethoxazole is commonly used in combination with trimethoprim (co-trimoxazole) for a wide range of bacterial infections but is not specifically used topically for *Pseudomonas* infections in burn cases.
- **Option C:** This option is not provided, but based on the correct answer, we can infer that the focus is on mafenide acetate.
- **Option D:** This option might represent another sulfonamide, but without specifics, it's clear that mafenide acetate is unique for its use in burn cases and activity against *Pseudomonas*.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that mafenide acetate can cause pain upon application and can interfere with carbonic anhydrase, potentially leading to metabolic acidosis, especially in extensive burns. Despite these side effects, its benefit in preventing *Pseudomonas* infections in burn patients makes it a valuable therapeutic option.

## **Correct Answer:** D. Mafenide acetate.