What is the best treatment approach for a patient with nasal colonization, particularly with bacteria such as Staphylococcus aureus (S. aureus) or Methicillin-resistant Staphylococcus aureus (MRSA), including those who are immunocompromised or elderly?

Treatment of Nasal Colonization

Do not routinely treat asymptomatic nasal colonization with S. aureus or MRSA; reserve decolonization for specific high-risk scenarios including recurrent skin infections, documented household transmission, or pre-operative screening before high-risk surgeries. 1, 2

When to Treat: Specific Indications

Decolonization should only be pursued in the following clinical scenarios:

• Recurrent skin and soft tissue infections (≥2 episodes at different anatomic sites over 6 months) that persist despite optimized wound care and hygiene measures 1, 2
• Ongoing household transmission among close contacts despite implementation of hygiene interventions 3, 1, 2
• Pre-operative screening and decolonization before high-risk surgeries such as cardiothoracic or orthopedic procedures 3
• Following treatment of active infection in symptomatic patients to prevent recurrence 1, 2

The Infectious Diseases Society of America and American College of Physicians explicitly recommend against routine decolonization of asymptomatic carriers, as this promotes resistance without proven clinical benefit in preventing infections 1, 2.

Standard Decolonization Protocol

Primary Regimen

• Mupirocin 2% ointment applied to both anterior nares twice daily for 5-10 days 3, 1, 2
• This is the first-line decolonization regimen recommended by the Infectious Diseases Society of America and European Society of Clinical Microbiology and Infectious Diseases 3, 2

Enhanced Protocol for Recurrent Cases

For patients with persistent recurrences despite initial decolonization:

• Mupirocin 2% ointment to anterior nares twice daily for 5-10 days PLUS 2
• Chlorhexidine gluconate 2% body wash for 5-14 days OR 3, 2
• Dilute bleach baths using 1/4 to 1/2 cup bleach per full bathtub 2

This combined approach targets both nasal and extra-nasal colonization sites 3, 2.

Essential Concurrent Hygiene Measures

Decolonization fails without simultaneous hygiene interventions—these are not optional adjuncts but mandatory components 3:

• Keep all draining wounds covered with clean, dry bandages 1, 2
• Practice rigorous hand hygiene with soap and water or alcohol-based gel after touching infected areas or contaminated items 1, 2
• Avoid sharing personal items such as towels, razors, or clothing 2
• Clean high-touch surfaces regularly with commercial cleaners 2
• Treat interdigital toe space infections or maceration to eliminate hidden colonization reservoirs 3, 2

Household Contact Management

• Evaluate all symptomatic household contacts first and treat any active infections before considering decolonization 1, 2
• Treat both the patient and household contacts simultaneously when ongoing transmission is documented, as this approach results in fewer recurrences than treating the patient alone 3, 2
• Asymptomatic household contacts should only be considered for decolonization when ongoing transmission is documented despite hygiene measures 3, 1, 2

Critical Pitfalls to Avoid

Resistance Development

• High-level mupirocin resistance has been reported in some S. aureus strains, particularly in community settings 3, 2
• Prolonged or indiscriminate use promotes resistance without clinical benefit 3, 2
• However, short courses of treatment, even when repeated, are associated with remarkably little clinically significant resistance 4

Recolonization Rates

• Recolonization occurs in 40-60% of patients within 3 months after decolonization 3
• While mupirocin effectively reduces nasal colonization in the short term, it has not conclusively been shown to prevent infections in community settings 2, 5

Inappropriate Screening

• Do not obtain screening cultures before or after decolonization in the absence of active infection 1, 2
• Pre-decolonization cultures are unnecessary if prior MRSA infection was documented 2
• Post-decolonization surveillance cultures are not recommended in the absence of active infection 2

Product-Specific Warnings

• Do not use mupirocin ointment intranasally—the FDA-approved mupirocin ointment is for topical skin use only; a separate intranasal formulation exists for nasal decolonization 6
• Avoid use in patients with moderate or severe renal impairment due to polyethylene glycol absorption risk 6

Evidence Quality Considerations

Mupirocin demonstrates 94% eradication rates compared to 44% with bacitracin at 72-96 hours, establishing clear superiority 7. In surgical populations, a 5-day course significantly reduced both MSSA (P=0.0341) and MRSA (P=0.0073) colonization rates on the day of surgery 8. However, large randomized trials have not demonstrated significant reduction in overall infection rates with prophylactic mupirocin, though subgroup analyses suggest benefit in selected populations with documented nasal carriage 5, 9.