Drug of choice for Methicillin resistant staphylococcus aureus is (MRSA) –
**Core Concept**
Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that has developed resistance to beta-lactam antibiotics, including methicillin. This resistance is due to the production of an altered penicillin-binding protein (PBP2a) that has a low affinity for beta-lactam antibiotics.
**Why the Correct Answer is Right**
The drug of choice for MRSA is vancomycin, a glycopeptide antibiotic that inhibits cell wall synthesis by binding to the D-alanyl-D-alanine terminus of cell wall precursors. This binding prevents the incorporation of these precursors into the bacterial cell wall, ultimately leading to cell lysis and death. Vancomycin is effective against MRSA because it can penetrate the bacterial cell wall and reach its target site.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a commonly used antibiotic for treating MRSA infections.
**Option B:** This option is incorrect because it is a beta-lactam antibiotic, which is ineffective against MRSA due to its resistance mechanism.
**Option C:** This option is incorrect because it is not a first-line treatment for MRSA infections.
**Clinical Pearl / High-Yield Fact**
Vancomycin is a time-dependent antibiotic, meaning its effectiveness depends on maintaining a sufficient concentration in the bloodstream for a prolonged period. This is why it's essential to monitor vancomycin levels and adjust dosages accordingly to ensure optimal treatment outcomes.
**Correct Answer: D. Vancomycin**