What is mupirocin?

Mupirocin: A Topical Antibiotic for Skin Infections and MRSA Decolonization

Mupirocin is a topical antibiotic that inhibits bacterial protein synthesis by binding to bacterial isoleucyl transfer-RNA synthetase, making it effective against a wide range of gram-positive bacteria, particularly Staphylococcus aureus including MRSA. 1

Formulation and Properties

• Available as a 2% ointment in a water-miscible polyethylene glycol base
• Unique chemical structure unrelated to other antibacterial agents
• Minimal systemic absorption (<1.1 nanogram/mL in blood) when applied topically
• Rapidly metabolized if absorbed systemically
• Active against:
  • Staphylococcus aureus (including MRSA)
  • Streptococcus pyogenes
  • Most strains of Staphylococcus epidermidis and Staphylococcus saprophyticus
  • Moderately active against some gram-negative bacteria 1, 2

Clinical Applications

1. Treatment of Skin Infections

• Pediatric use: Recommended for minor skin infections (impetigo) and secondarily infected skin lesions (eczema, ulcers, lacerations) in children 3
• Applied 2-3 times daily for 5-10 days
• Clinical efficacy typically shows >90% bacterial eradication and >80% clinical cure rates in primary and secondary skin infections 2, 4

2. MRSA Decolonization

• Nasal decolonization: Applied to anterior nares twice daily for 5-10 days
  • 10-dose regimen (twice daily for 5 days) achieves 89.5% decolonization for at least four weeks 5
• Particularly important for:
  • Patients with recurrent MRSA infections
  • Healthcare settings to prevent transmission
  • Pre-operative prophylaxis for high-risk surgeries 5

Resistance Considerations

• Resistance mechanisms:
  • Low-level resistance (MIC 8-256 mg/L): Point mutation in native IleRS
  • High-level resistance (MIC ≥512 mg/L): Acquisition of mupA gene on mobile genetic elements 6
• Risk factors for resistance development:
  • Unrestricted over-the-counter use
  • Treatment of chronic wounds/pressure sores
  • Increased selective pressure from widespread use 6

Best Practices for MRSA Decolonization

1. Combination approach:

   • Intranasal mupirocin 2% ointment twice daily for 5-10 days
   • PLUS topical antiseptic body decolonization (chlorhexidine washes or dilute bleach baths) 5

2. Hygiene measures (essential for successful decolonization):

   • Regular bathing and hand hygiene
   • Covering draining wounds with clean bandages
   • Avoiding sharing personal items
   • Cleaning high-touch surfaces 5

3. For recurrent infections:

   • Consider monthly application of mupirocin (5-day course each month) which can reduce recurrent infections by approximately 50% 5
   • Evaluate household contacts for evidence of S. aureus infection if transmission continues 5

Common Pitfalls and Caveats

• Using mupirocin alone without addressing body colonization or environmental factors may lead to treatment failure 5
• Not recommended for long-term or repeated use due to risk of resistance development
• Side effects are minimal, limited to local reactions in less than 3% of patients 7
• Screening cultures prior to decolonization are not routinely recommended if prior MRSA infection was documented 5
• Tetracyclines should not be used in children <8 years of age when treating associated skin infections 3

Mupirocin represents an important topical antibiotic option for treating superficial skin infections and MRSA decolonization, with the advantage of minimal systemic absorption and a unique mechanism of action that limits cross-resistance with other antibiotics.