What is the recommended treatment for nasal MRSA (Methicillin-resistant Staphylococcus aureus) colonization using mupirocin nasal ointment?

Mupirocin Nasal Ointment for MRSA Decolonization

Apply mupirocin 2% nasal ointment into each nostril twice daily for 5 days to effectively decolonize nasal MRSA carriage, particularly before cardiac and orthopedic surgery where it provides a strong mortality and morbidity benefit. 1

Standard Dosing Protocol

• Apply approximately 0.5 grams (about the size of a matchhead) of mupirocin 2% ointment into each nostril twice daily for 5 days 1, 2
• The 10-dose regimen (twice daily for 5 days) is superior to shorter 6-dose regimens, maintaining decolonization for at least 4 weeks after therapy (89.5% vs 68.0% success rate, p=0.016) 3
• For recurrent skin and soft tissue infections, consider monthly 5-day courses, which reduce nasal colonization by 73% and skin infections by 58% over one year 2

Surgical Context: Strongest Evidence for Benefit

For patients undergoing cardiac or orthopedic surgery, mupirocin decolonization provides a strong recommendation with moderate certainty of evidence, reducing Staphylococcus aureus infectious complications by 45% (RR 0.55,95% CI 0.34-0.89). 1, 2

Timing Considerations:

• Complete the 5-day decolonization course 1-2 weeks before surgery, ideally starting at least 48 hours preoperatively 1, 2
• If the 5-day course cannot be completed preoperatively, finish it postoperatively 1
• For elective surgery, consider postponing the procedure to complete decolonization if feasible and posing no additional patient risk 1

Enhanced Decolonization Strategy

Combine mupirocin with chlorhexidine for comprehensive decolonization, which significantly reduces nasal MRSA carriage (RR 0.63,95% CI 0.52-0.75). 2

Combination Protocol:

• Mupirocin 2% nasal ointment twice daily for 5 days PLUS 1
• Chlorhexidine gluconate soap (40 mg/mL) for daily body washing for 5-14 days 1
• OR dilute bleach baths: 1 teaspoon per gallon of water (¼ cup per ¼ tub) for 15 minutes twice weekly for 3 months 1

Recurrent Skin and Soft Tissue Infections

Decolonization should only be considered after optimizing hygiene measures, as mupirocin has not conclusively been shown to prevent infections in all MRSA carriers. 1

When to Consider Decolonization:

• Patient develops recurrent SSTI despite optimizing wound care and hygiene measures 1
• Ongoing transmission occurring among household members despite hygiene interventions 1
• Always reinforce hygiene measures concurrently with decolonization 1

Important Caveat:

While mupirocin effectively reduces nasal colonization, evidence for preventing first-time skin infections in community settings is limited—one trial showed mupirocin decreased nasal colonization but did not reduce the incidence of first-time SSTI compared to placebo 1

Critical Limitations and Resistance Concerns

Mupirocin effectiveness is significantly compromised by resistance: low-level mupirocin resistance (prevalence 23% in some settings) is strongly associated with treatment failure (p=0.003). 4

Resistance Patterns:

• High-level mupirocin resistance results in only 27.7% clearance on day 3 post-treatment, compared to 78.5% for susceptible strains 5
• Sustained culture negativity at 1-4 weeks occurs in 91% with susceptible MRSA but only 25% with resistant strains 5
• In endemic MRSA settings (not outbreak situations), mupirocin achieves only 25% eradication of multisite MRSA carriage versus 18% with placebo—a marginal benefit (RR 0.72,95% CI 0.33-1.55) 4

Stewardship Considerations:

• Monitor local mupirocin resistance rates in colonizing and infecting isolates 1
• Universal decolonization without screening should be applied cautiously as it may promote mupirocin resistance 1
• Consider susceptibility testing before implementing mupirocin in infection control programs, particularly in endemic settings 5, 4

Household and Contact Management

When household transmission is suspected, evaluate all contacts for active infection and treat symptomatic individuals; consider decolonization of asymptomatic contacts only after treating active infections. 1

• Symptomatic contacts require evaluation and treatment before considering decolonization 1
• Nasal and topical body decolonization of asymptomatic household contacts may be considered 1
• Personal and environmental hygiene measures are mandatory for all contacts 1

Practical Implementation Notes

• Screening cultures prior to decolonization are not routinely needed if at least one prior infection was documented as MRSA 1
• Surveillance cultures following decolonization are not routinely recommended in the absence of active infection 1
• No emergence of multidrug-resistant bacteria has been observed due to decolonization selection pressure 2
• The American College of Surgeons notes that routine decolonization without prior microbiological screening is more cost-effective than selective treatment for surgical patients 2