Amoxicillin Treatment Failure Revealing Community-associated Methicillin-resistant Staphylococcus aureus in an 11-year-old Swimmer with Nonodontogenic Labial Abscess.

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) is an emerging cause of skin and soft tissue infections in otherwise healthy pediatric populations. Empirical beta-lactam therapy failure may delay appropriate management, particularly in community-exposed individuals. An 11-year-old competitive swimmer presented with progressive lower lip swelling and purulent discharge unresponsive to amoxicillin therapy. Clinical examination revealed a solitary pustular lesion with significant edema on the lower vermilion border. Microbiological culture confirmed MRSA resistant to beta-lactams but susceptible to clindamycin and gentamicin. The patient was treated with local debridement, antisepsis, systemic clindamycin, and topical gentamicin, resulting in complete resolution within 10 days. This case emphasizes the importance of microbiological evaluation in persistent labial abscesses in pediatric patients, particularly in the context of rising antimicrobial resistance.