What is a recommended first-line antibiotic for outpatient treatment of skin and soft tissue infections?

First-Line Antibiotic for Outpatient Treatment of Skin and Soft Tissue Infections

For outpatient treatment of skin and soft tissue infections, dicloxacillin or cephalexin is recommended as first-line therapy for non-purulent infections, while trimethoprim-sulfamethoxazole (TMP-SMX) is recommended for purulent infections where MRSA is suspected. 1

Treatment Algorithm Based on Infection Type

Non-Purulent Skin and Soft Tissue Infections

These infections are typically caused by streptococci and methicillin-susceptible Staphylococcus aureus (MSSA).

1. First-line options:

   • Dicloxacillin: 500 mg PO four times daily 1
   • Cephalexin: 500 mg PO four times daily 1

2. Alternative options (penicillin-allergic patients):

   • Clindamycin: 300-450 mg PO three times daily 1
   • Erythromycin: 250 mg PO four times daily (note: increasing resistance) 1

Purulent Skin and Soft Tissue Infections

These infections often involve abscesses and are frequently caused by S. aureus, including MRSA.

1. First-line options when MRSA is suspected:

   • TMP-SMX: 1-2 double-strength tablets PO twice daily 1
   • Doxycycline: 100 mg PO twice daily (adults) 1

2. Alternative options:

   • Clindamycin: 300-450 mg PO three times daily (if susceptible) 1
   • Minocycline: 200 mg loading dose, then 100 mg PO twice daily 1

Special Considerations

MRSA Coverage

When community-acquired MRSA is prevalent or suspected (e.g., presence of abscess, previous MRSA infection, or failed beta-lactam therapy):

• TMP-SMX is particularly effective and is recommended as first-line therapy 1
• Clindamycin can be used when susceptibility is confirmed 1

Duration of Therapy

• Typical course: 5-10 days 1
• Duration should be guided by clinical response 1

Pediatric Considerations

• Dosing adjustments are required for children
• Doxycycline is not recommended for children under 8 years 1

Pitfalls and Caveats

1. Antibiotic Resistance:

   • Be aware of local resistance patterns, particularly for S. aureus
   • Some strains of S. aureus and S. pyogenes may be resistant to erythromycin 1
   • Clindamycin may have inducible resistance in erythromycin-resistant strains 1

2. Incision and Drainage:

   • For simple abscesses, incision and drainage alone may be sufficient without antibiotics 1
   • Antibiotics should be added for abscesses with surrounding cellulitis, systemic symptoms, or in immunocompromised patients

3. Treatment Failure:

   • Consider MRSA if initial therapy with beta-lactams fails
   • Obtain cultures in treatment failures or severe infections
   • Consider broader coverage for complicated infections or in immunocompromised patients

4. Oral vs. Parenteral Therapy:

   • Reserve parenteral therapy for severe infections requiring hospitalization
   • Linezolid (600 mg PO twice daily) can be considered for outpatient MRSA infections when other options fail, but is expensive and has more side effects 1, 2

By following this evidence-based approach to selecting antibiotics for skin and soft tissue infections, clinicians can optimize treatment outcomes while minimizing unnecessary broad-spectrum antibiotic use.