**Core Concept**
Impetigo is a superficial skin infection caused by Staphylococcus aureus or Streptococcus pyogenes. Effective treatment involves antibiotics that target these bacteria, often penicillins or cephalosporins.

**Why the Correct Answer is Right**
Dicloxacillin is a penicillinase-resistant penicillin that effectively treats Staphylococcus aureus infections, including impetigo. It works by inhibiting cell wall synthesis in bacteria through the enzyme transpeptidase, ultimately leading to bacterial cell death. Dicloxacillin is also effective against beta-lactamase-producing Staphylococcus aureus strains, making it a suitable choice for treating impetigo.

**Why Each Wrong Option is Incorrect**
* **Option B:** Ciprofloxacin is a fluoroquinolone antibiotic, which is not the preferred choice for treating impetigo due to its limited activity against Staphylococcus aureus and potential side effects.
* **Option C:** Gentamycin is an aminoglycoside antibiotic, which is not typically used to treat superficial skin infections like impetigo due to its potential for ototoxicity and nephrotoxicity.
* **Option D:** Amoxicillin and clavulanic acid is a combination antibiotic that is effective against a broad range of bacteria, but it is not the preferred choice for treating impetigo due to the emergence of beta-lactamase-producing strains that may be resistant to this combination.

**Clinical Pearl / High-Yield Fact**
When choosing an antibiotic for impetigo, it's essential to consider the local epidemiology of Staphylococcus aureus and Streptococcus pyogenes resistance patterns to ensure effective treatment.

**✓ Correct Answer: A. Dicloxacillin**