What are the treatment options for skin infections?

Treatment Options for Skin Infections

For most uncomplicated skin infections, oral antibiotics targeting streptococci are the first-line treatment, with beta-lactams like cephalexin, dicloxacillin, or amoxicillin-clavulanate being preferred for 5 days if clinical improvement occurs. 1

Classification Framework

Before selecting treatment, classify the infection by:

• Purulent vs. non-purulent character 1
• Anatomical depth (superficial dermis vs. deep fascia/muscle) 1
• Severity (mild outpatient vs. severe requiring hospitalization) 1
• Presence of systemic toxicity (fever, hypotension, tachycardia) 1

Mild Uncomplicated Infections (Outpatient)

Non-Purulent Cellulitis/Erysipelas

Beta-lactam monotherapy is recommended since MRSA is an uncommon cause of typical cellulitis (successful in 96% of cases with cefazolin/oxacillin). 1

Oral options:

• Cephalexin 500 mg three times daily 1
• Dicloxacillin 500 mg four times daily 1
• Amoxicillin 500 mg three times daily 1
• Clindamycin 300 mg three times daily 1

Duration: 5 days if clinical improvement occurs; otherwise extend to 7-10 days 1, 2

Avoid MRSA coverage unless: penetrating trauma (especially IV drug use), purulent drainage, or concurrent MRSA infection elsewhere 1

Purulent Infections (Abscesses, Furuncles)

Primary treatment is incision and drainage - antibiotics may be unnecessary for simple abscesses after adequate drainage. 1

Add antibiotics if:

• Multiple lesions 1
• Severe or extensive disease 1
• Rapid progression with surrounding cellulitis 1
• Immunosuppression 1
• Lack of response to drainage alone 1

Empiric MRSA coverage options (oral):

• Trimethoprim-sulfamethoxazole 160-800 mg twice daily 1
• Doxycycline 100 mg twice daily 1
• Clindamycin 300 mg three times daily 1

If streptococcal coverage also needed: Clindamycin alone OR combine TMP-SMX/doxycycline with a beta-lactam (amoxicillin, cephalexin) 1

Duration: 5-7 days 1

Superficial Infections (Impetigo)

Topical therapy for limited disease:

• Mupirocin 2% ointment three times daily (78% efficacy in pediatric impetigo) 1, 2

Systemic therapy for extensive disease:

• Same oral agents as cellulitis above 1

Moderate to Severe Infections (Hospitalized)

Complicated Skin and Soft Tissue Infections

Empiric IV therapy should cover MRSA plus gram-negatives/anaerobes: 1

Recommended regimens:

• Vancomycin 30 mg/kg/day in 2 divided doses PLUS piperacillin-tazobactam 3.37 g every 6-8 hours 1
• Vancomycin PLUS ampicillin-sulbactam 1.5-3 g every 6-8 hours 1
• Vancomycin PLUS carbapenem (ertapenem 1 g daily, meropenem 1 g every 8 hours, or imipenem 1 g every 6-8 hours) 1

Alternative MRSA agents:

• Linezolid 600 mg IV/PO twice daily 1
• Daptomycin 4 mg/kg IV once daily 1
• Telavancin 10 mg/kg IV once daily 1

Duration: 7-14 days based on clinical response 1

Necrotizing Infections

Urgent surgical exploration and debridement is mandatory - this takes priority over antibiotics. 1

Empiric broad-spectrum therapy:

• Vancomycin PLUS piperacillin-tazobactam, ampicillin-sulbactam, or carbapenem 1

Pathogen-specific therapy once identified:

• Streptococcal: Penicillin 2-4 million units every 4-6 hours PLUS clindamycin 600-900 mg every 8 hours 1
• Clostridial (gas gangrene): Clindamycin 600-900 mg every 8 hours PLUS penicillin 2-4 million units every 4-6 hours 1
• Staphylococcal: Nafcillin/oxacillin 1-2 g every 4 hours OR vancomycin for MRSA 1
• Aeromonas/Vibrio (water exposure): Doxycycline 100 mg every 12 hours PLUS ceftriaxone 1-2 g every 24 hours 1

Special Circumstances

Animal/Human Bites

Preemptive antibiotics (3-5 days) for: immunocompromised, asplenic, advanced liver disease, hand/face injuries, or joint capsule penetration 1

Recommended agent: Amoxicillin-clavulanate 500-875 mg twice daily (covers Pasteurella, streptococci, staphylococci, anaerobes) 1

Alternatives:

• Doxycycline 100 mg twice daily (excellent Pasteurella activity but some streptococcal resistance) 1
• Moxifloxacin 400 mg daily 1

Always update tetanus vaccination if >10 years since last dose 1

Diabetic Foot Infections

Mild infections: Same oral agents as uncomplicated cellulitis 1

Moderate-severe infections:

• Ertapenem 1 g daily 1
• Piperacillin-tazobactam 1
• Moxifloxacin 400 mg daily 1
• Linezolid 600 mg twice daily for MRSA 1

Pediatric Considerations

Avoid tetracyclines in children <8 years 1

Hospitalized children with complicated SSTI:

• Vancomycin 15 mg/kg/dose every 6 hours 1
• Clindamycin 10-13 mg/kg/dose every 6-8 hours (if local resistance <10%) 1
• Linezolid 10 mg/kg/dose every 8 hours for children <12 years 1

Minor infections: Mupirocin 2% topical ointment 1

Common Pitfalls

Do not routinely culture non-purulent cellulitis unless severe systemic features, immunocompromised, or unusual exposures (water immersion, animal bites) 1

Do not use rifampin as monotherapy or adjunctive therapy for skin infections 1

Do not prescribe antibiotics for simple abscesses after adequate drainage unless high-risk features present 1

Do not treat for 10+ days routinely - this represents avoidable antibiotic exposure in 42% of cases; 5-7 days is sufficient for most infections 1, 2, 3

Recognize treatment failure early: If no improvement after 5 days, reassess for deeper infection, abscess formation, or resistant organisms 1, 2