What antibiotic cream (Abx) is recommended for a patient with potentially infected shoulder sores?

Topical Antibiotic Treatment for Shoulder Sores

For potentially infected shoulder sores, mupirocin 2% ointment applied twice daily for 5 days is the first-line topical antibiotic, providing excellent coverage against both Staphylococcus aureus (including MSSA) and Streptococcus pyogenes, the primary pathogens in skin infections. 1, 2

When Topical Antibiotics Are Appropriate

• Topical antibiotics should only be used for localized, superficial skin infections without systemic signs such as fever, extensive erythema beyond the immediate wound area, or purulent drainage suggesting deeper infection 3
• If the sores show signs of cellulitis (spreading erythema, warmth, tenderness extending beyond the wound margins), systemic oral antibiotics are required instead of topical therapy 4
• Any fluctuant collection or abscess requires incision and drainage as primary treatment, with antibiotics playing only a subsidiary role 3, 4

First-Line Topical Antibiotic Selection

• Mupirocin 2% ointment applied twice daily for 5 days is the gold standard topical antibiotic for superficial skin infections, demonstrating superior or equivalent efficacy compared to oral cephalexin, oral erythromycin, and other topical agents 1, 2, 5
• Mupirocin has excellent in vitro activity against staphylococci and most streptococci, with over 90% bacterial eradication rates in clinical trials 2
• The cream formulation of mupirocin may improve patient compliance and has been shown to be as effective as or superior to the ointment formulation 1

Alternative Topical Options

• Retapamulin 1% ointment applied twice daily for 5 days is FDA-approved for impetigo in adults and children ≥9 months, covering methicillin-susceptible S. aureus and S. pyogenes 6
• Retapamulin should be applied as a thin layer to affected areas up to 100 cm² in adults, with the treated area optionally covered with sterile bandage 6
• Fusidic acid cream is an alternative with excellent activity against S. aureus including some methicillin-resistant strains, though it has lower activity against streptococci compared to mupirocin 1, 7, 8

When to Escalate to Systemic Therapy

• If the shoulder sores show any of the following, switch immediately to oral or IV antibiotics rather than topical treatment: 3, 4

  • Spreading erythema beyond 2-3 cm from the wound edge
  • Systemic signs (fever >38°C, chills, malaise)
  • Purulent drainage suggesting deeper infection
  • Failure to improve after 48 hours of topical therapy
  • Immunocompromised status or diabetes

• For non-purulent cellulitis requiring systemic therapy, cephalexin 500 mg orally four times daily for 5 days is first-line 4

• For purulent infections or MRSA risk factors (penetrating trauma, injection drug use, known MRSA colonization), clindamycin 300-450 mg orally four times daily provides coverage for both streptococci and MRSA 4

Treatment Duration and Monitoring

• Treat for exactly 5 days if clinical improvement occurs, extending only if symptoms have not improved within this timeframe 3, 4, 6
• Reassess within 24-48 hours to verify clinical response, as treatment failure rates of 21% have been reported with some regimens 4
• Discontinue topical antibiotic immediately if severe local irritation or sensitization occurs, wipe off the ointment, and institute alternative therapy 6

Critical Pitfalls to Avoid

• Never use topical antibiotics for deep or extensive infections—they penetrate poorly beyond superficial layers and will lead to treatment failure 3
• Do not use retapamulin on mucosal surfaces (nasal, oral, ophthalmic, intravaginal), as efficacy and safety have not been established and epistaxis has been reported with nasal use 6
• Avoid bacitracin for chronic or recurring wounds due to high rates of treatment failure and sensitization 7
• Do not continue ineffective topical therapy beyond 48 hours—progression despite appropriate treatment indicates either resistant organisms or deeper infection requiring systemic antibiotics 4

Adjunctive Measures

• Examine for predisposing factors such as underlying skin conditions, poor hygiene, or trauma that may have caused the sores 3
• If recurrent S. aureus infections occur, consider a 5-day decolonization regimen with intranasal mupirocin twice daily, daily chlorhexidine washes, and decontamination of personal items 3
• Ensure proper wound care with gentle cleansing and coverage with sterile dressing if desired 6