A 6-year-old boy from Mumbai presents with a 3-day history of impetigo on his left leg with honey-crusted lesions and surrounding erythema. Gram stain of the pustular fluid shows gram-positive cocci in chains. Culture confirms group A Streptococcus (GAS). The child has no systemic toxicity, normal renal function, and no signs of cellulitis or lymphangitis. What is the most appropriate next step in management?

Explanation

## Streptococcal Impetigo: Topical vs. Systemic Therapy **Key Point:** Non-bullous impetigo caused by GAS without signs of systemic infection or cellulitis is best managed with topical antibiotics as first-line therapy. **High-Yield:** The 2016 American Academy of Dermatology (AAD) and 2014 IDSA guidelines recommend: - **Topical antibiotics** (mupirocin) for localized, non-bullous impetigo without systemic signs - **Systemic antibiotics** reserved for: - Bullous impetigo - Extensive lesions (>5 lesions or covering >2% body surface area) - Signs of cellulitis, lymphangitis, or systemic toxicity - Immunocompromised patients - Failed topical therapy ### Topical vs. Systemic Therapy Comparison | Feature | Topical Mupirocin | Oral Amoxicillin | IM Benzathine PCN | IV Ceftriaxone | |---------|-------------------|------------------|-------------------|----------------| | **Indication** | Localized non-bullous impetigo | Extensive/systemic signs | Prophylaxis/severe GAS | Severe/invasive | | **Efficacy** | 90% cure in 7 days | Good | N/A for impetigo | Overkill | | **Resistance** | Rare (<5%) | None | N/A | None | | **Cost** | Low | Low | Moderate | High | | **Compliance** | Better (topical) | Good | Single dose | Hospitalization | | **First-line for localized?** | **YES** | No | No | No | **Clinical Pearl:** Mupirocin has superior cure rates for impetigo compared to systemic antibiotics in non-bullous cases and reduces transmission to contacts. **Warning:** Overuse of systemic antibiotics for simple impetigo contributes to antibiotic resistance and unnecessary drug exposure. ### Decision Algorithm ```mermaid flowchart TD A[GAS impetigo diagnosed]:::outcome --> B{Bullous or extensive?}:::decision B -->|No, localized| C{Systemic signs?}:::decision B -->|Yes| D[Systemic antibiotics]:::action C -->|No| E[Topical mupirocin TID × 7 days]:::action C -->|Yes| F[Oral amoxicillin or cephalexin]:::action E --> G[Expected cure in 7 days]:::outcome F --> H[Monitor for complications]:::action ``` **Mnemonic:** **TOPICAL-FIRST** — Topical antibiotics are first-line for localized, non-bullous impetigo without systemic signs.