What is the best antibiotic for treating nasal colonization of Staphylococcus (S.) aureus, a gram-positive coccus in pairs?

Best Antibiotic for Nasal Colonization of Gram-Positive Cocci in Pairs

For nasal colonization with Staphylococcus aureus (gram-positive cocci in pairs/clusters), topical mupirocin 2% ointment applied to both anterior nares twice daily for 5-10 days is the recommended first-line treatment when decolonization is indicated. 1, 2

When Decolonization is Actually Indicated

Not all patients with nasal S. aureus colonization require treatment. Decolonization should only be pursued in specific clinical scenarios:

• Recurrent skin and soft tissue infections despite optimized wound care and hygiene measures 1, 2
• Ongoing household transmission among close contacts despite hygiene interventions 1, 2
• During outbreak control in sports teams or institutional settings to limit spread 3
• Following treatment of active infection in symptomatic patients 2

Routine decolonization of asymptomatic carriers is NOT recommended by the Infectious Diseases Society of America 1, 2

First-Line Treatment Protocol

Nasal Decolonization

Mupirocin 2% ointment is the standard of care:

• Apply to both anterior nares twice daily for 5-10 days 1, 2
• Efficacy rates of approximately 90-95% for initial clearance 4, 5
• Superior to bacitracin (94% vs 44% eradication at 72-96 hours) 4

Body Decolonization (For Recurrent Cases)

Combine nasal mupirocin with topical body decolonization 1, 2:

• Chlorhexidine gluconate 2% body wash daily for 5-14 days 1, 2, OR
• Dilute bleach baths (1/4 to 1/2 cup bleach per full bathtub) for 15 minutes twice weekly for up to 3 months 1, 2

Alternative Agents When Mupirocin Fails or is Unavailable

For Mupirocin-Resistant Strains

High-level mupirocin resistance (MIC >512 µg/mL) has been increasingly reported, particularly in MRSA strains 3, 6:

• Systemic clindamycin: 100% eradication at both early and late follow-up in one study 7
• Systemic ofloxacin: 95% eradication at early follow-up, 100% at late follow-up 7
• Triple antibiotic ointment (TAO): 53.3% decolonization rate for methicillin-susceptible S. aureus, though less effective than mupirocin 8
• Retapamulin: Active against S. aureus including methicillin-susceptible strains, though primarily studied for skin infections rather than colonization 9, 10

Comparative Efficacy of Systemic Options

Among systemic antibiotics studied for nasal decolonization 7:

• Clindamycin and ofloxacin showed superior long-term efficacy
• Dicloxacillin, erythromycin, and cephalosporins achieved only 50% or less eradication at late follow-up
• Fluoroquinolones (enoxacin, fleroxacin) showed promise but limited data

Essential Concurrent Hygiene Measures

All patients undergoing decolonization must implement strict hygiene practices 1, 2:

• Keep draining wounds covered with clean, dry bandages 2
• Hand hygiene with soap and water or alcohol-based sanitizer after touching infected areas 1, 2
• Avoid sharing personal items (towels, razors, clothing) 1, 2
• Clean high-touch household surfaces regularly 1, 2
• Treat interdigital toe space infections/maceration to reduce colonization reservoirs 2

Household Contact Management

When ongoing transmission is documented 1, 2:

• Evaluate and treat symptomatic contacts for active infection first 1, 2
• Consider simultaneous decolonization of asymptomatic household contacts 1, 2
• Recent evidence shows treating both patient and household contacts together reduces recurrences compared to treating the patient alone 2

Critical Pitfalls and Limitations

Resistance Concerns

• Avoid prolonged or indiscriminate mupirocin use to prevent resistance development 2, 6
• High-level mupirocin resistance occurs more frequently in methicillin-resistant than methicillin-susceptible staphylococci 6
• Mupirocin resistance has been associated with subsequent decolonization failure 3

Temporary Clearance

• Recolonization is common within several months after discontinuation 1, 5
• Mupirocin effectively reduces nasal colonization but has not conclusively been shown to prevent infections in community settings 2, 5

Monitoring

• Routine surveillance cultures following decolonization are NOT recommended in the absence of active infection 1, 2
• Pre-decolonization cultures are unnecessary if prior MRSA infection was documented 1, 2

Safety Considerations

• Hexachlorophane should not be used in children under 2 months of age due to neurological complications risk 1
• Mupirocin is highly protein bound (>97%), and the effect of wound secretions on efficacy has not been determined 6