What is the recommended treatment and dosage duration for Methicillin-resistant Staphylococcus aureus (MRSA) in the nares?

Treatment of MRSA Nasal Colonization

For MRSA nasal colonization, mupirocin 2% ointment applied to the anterior nares twice daily for 5 days is the recommended treatment regimen. 1

Treatment Protocol

First-line Treatment:

• Mupirocin 2% nasal ointment
  • Dosage: Apply to both anterior nares twice daily
  • Duration: 5 days
  • Application technique: Place a small amount (approximately pea-sized) of ointment on a cotton swab and coat the inside of each nostril

Efficacy and Evidence:

• Mupirocin has been shown to effectively eradicate MRSA nasal colonization in approximately 90% of cases immediately after treatment 2
• For mupirocin-susceptible MRSA strains, sustained clearance rates of 91% have been observed 2
• The 5-day, twice-daily regimen (10 doses total) is superior to shorter regimens, with 89.5% of patients remaining decolonized for at least four weeks after treatment compared to only 68% with 6-dose regimens 3

Comprehensive Decolonization Strategy

For patients with recurrent MRSA infections or ongoing transmission despite initial treatment, a more comprehensive approach may be needed:

1. Nasal decolonization with mupirocin twice daily for 5 days
2. PLUS concurrent topical body decolonization with:
   • Chlorhexidine body washes daily for 5-14 days, OR
   • Dilute bleach baths (1/4-1/2 cup bleach per full bath) 1

Maintenance Therapy for Recurrent Cases

For patients with recurrent MRSA skin infections despite initial decolonization:

• Monthly application of mupirocin ointment (5-day course each month) may be considered 1, 4
• This regimen has been shown to reduce recurrent infections by approximately 50% 1
• Alternative: Oral clindamycin 150 mg daily for 3 months, which can decrease subsequent infections by about 80% in cases of susceptible S. aureus 1

Additional Hygiene Measures

Always combine antimicrobial treatment with the following measures:

• Keep draining wounds covered with clean, dry bandages
• Maintain good personal hygiene with regular bathing
• Clean hands regularly with soap and water or alcohol-based hand gel
• Avoid sharing personal items (razors, towels, linens)
• Clean high-touch surfaces with appropriate cleaners 1

Important Considerations and Caveats

• Resistance concerns: Mupirocin resistance has been reported, with high-level resistance associated with treatment failure. Only 27.7% of patients with high-level mupirocin-resistant MRSA achieve negative cultures after treatment 2
• Testing: Consider susceptibility testing for mupirocin if there is a history of repeated use or treatment failure
• Alternative agents: Triple antibiotic ointment may be considered as an alternative when mupirocin resistance is suspected, though efficacy is lower (53.3% decolonization rate) 5
• Duration of effect: Without maintenance therapy, recolonization commonly occurs within 4-12 weeks after initial clearance 4, 6

By following this treatment protocol and comprehensive decolonization strategy, MRSA nasal colonization can be effectively managed, reducing the risk of subsequent infections and transmission to others.