First-line topical therapy for impetigo is which agent?

• A. Hydrocortisone cream
• B. Mupirocin (Bactroban)
• C. Erythromycin only
• D. Antifungal cream

Answer: (B)

Impetigo is a shallow bacterial skin infection caused most often by Staphylococcus aureus or Streptococcus pyogenes. For localized disease, applying a topical antibiotic directly to the lesions is the preferred first step because it quickly reduces the bacterial load on the skin and minimizes contagious spread.

Mupirocin ointment is the best choice because it specifically targets the bacteria commonly responsible for impetigo by inhibiting bacterial isoleucyl-tRNA synthetase, which blocks protein synthesis. This makes it highly effective for localized, superficial infections and allows easy, direct application to the affected areas with minimal systemic effects.

Hydrocortisone cream is a corticosteroid and does not treat bacterial infection; using it alone can potentially worsen or mask impetigo. Erythromycin can be used in some scenarios but is not the first-line topical option in many guidelines due to resistance and availability concerns. Antifungal cream targets fungal infections, not bacterial impetigo, so it wouldn’t be appropriate here.