**Core Concept**
Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that is resistant to many antibiotics, making it a significant concern in healthcare settings. The treatment of MRSA infections requires the use of antibiotics that are effective against this resistant strain.

**Why the Correct Answer is Right**
The drug of choice for treating MRSA infections is vancomycin, a glycopeptide antibiotic that inhibits cell wall synthesis by binding to the D-Ala-D-Ala terminus of the bacterial cell wall precursor. This binding prevents the incorporation of the cell wall precursors into the bacterial cell wall, ultimately leading to cell lysis and death. Vancomycin has been shown to be effective against MRSA strains, including those resistant to other antibiotics.

**Why Each Wrong Option is Incorrect**
**Option A:** Methicillin is incorrect because it is a type of penicillin antibiotic that is ineffective against MRSA due to the presence of the mecA gene, which encodes a modified penicillin-binding protein that confers resistance to methicillin and other beta-lactam antibiotics.
**Option B:** Ciprofloxacin is incorrect because it is a fluoroquinolone antibiotic that is not effective against MRSA, as the mecA gene also confers resistance to this class of antibiotics.
**Option C:** Linezolid is incorrect because while it is effective against MRSA, it is not the first-line treatment due to its potential side effects and higher cost compared to vancomycin.

**Clinical Pearl / High-Yield Fact**
Vancomycin is often administered in a divided dose, with a loading dose given initially to rapidly achieve therapeutic levels, followed by a maintenance dose to maintain steady-state levels.

**Correct Answer: C. Linezolid**