What is the appropriate treatment for skin and soft tissue infections?

Treatment of Skin and Soft Tissue Infections

The appropriate treatment for skin and soft tissue infections depends critically on classification into uncomplicated versus complicated infections, with uncomplicated infections requiring antibiotics targeting Staphylococcus and Streptococcus (or drainage alone for simple abscesses), while complicated infections demand broad-spectrum empiric antibiotics plus urgent surgical consultation for debridement. 1

Classification Framework

Before initiating treatment, classify the infection using these independent parameters 1:

• Necrotizing versus non-necrotizing character
• Anatomical depth (superficial: epidermis/dermis vs. deep: fascia/muscle)
• Purulent versus non-purulent characteristics
• Clinical severity using the Eron classification 1:
  • Class 1: No systemic toxicity or comorbidities
  • Class 2: Systemically unwell OR significant comorbidity (diabetes, obesity)
  • Class 3: Toxic appearance (fever, tachycardia, tachypnea, hypotension)
  • Class 4: Sepsis syndrome or life-threatening infection (necrotizing fasciitis)

Uncomplicated SSTIs

For uncomplicated infections (cellulitis, simple abscesses, impetigo, furuncles), treatment targets Staphylococcus aureus and Streptococcus pyogenes. 1

Simple Abscesses

• Incision and drainage is the primary treatment; antibiotics are NOT routinely indicated 1
• Add antibiotics only when 1:
  • Erythema and induration extend >5 cm from wound edge
  • Significant systemic response present
  • Patient has comorbidities or immunosuppression

Non-purulent Cellulitis/Erysipelas

Empiric oral antibiotic options 2, 3:

• First-generation cephalosporins (cephalexin 500 mg every 6 hours)
• Dicloxacillin
• Amoxicillin-clavulanate
• For penicillin allergy: Clindamycin or doxycycline

MRSA Coverage (when suspected)

Use when risk factors present (prior MRSA, injection drug use, recent hospitalization) 2:

• Trimethoprim-sulfamethoxazole (preferred)
• Doxycycline (monitor closely—21% treatment failure rate; re-evaluate in 24-48 hours) 2
• Clindamycin (note: 50% of MRSA strains have resistance) 2

Complicated SSTIs

Complicated infections require hospitalization, broad-spectrum IV antibiotics, and surgical consultation. 1

Initial Empiric Therapy

For severe infections with systemic toxicity, initiate broad polymicrobial coverage immediately 1:

Recommended regimens 1:

• Vancomycin 15 mg/kg every 12 hours IV PLUS one of:
  • Piperacillin-tazobactam 3.375 g every 6 hours or 4.5 g every 8 hours IV
  • Carbapenem (imipenem-cilastatin 500 mg every 6 hours, meropenem 1 g every 8 hours, or ertapenem 1 g every 24 hours)
  • Ceftriaxone 1 g every 24 hours PLUS metronidazole 500 mg every 8 hours IV

Necrotizing Fasciitis/Gas Gangrene

These are surgical emergencies requiring immediate intervention 1:

1. Urgent surgical exploration and debridement (strong recommendation) 1
2. Empiric broad-spectrum antibiotics 1:
   • Vancomycin PLUS piperacillin-tazobactam, ampicillin-sulbactam, or carbapenem
3. For documented Group A Streptococcus: Penicillin PLUS clindamycin 1
4. For clostridial myonecrosis: Penicillin PLUS clindamycin 1

Surgical Site Infections

Antibiotic selection based on surgical location 1:

Intestinal/genitourinary surgery 1:

• Ticarcillin-clavulanate, piperacillin-tazobactam, or carbapenem
• OR ceftriaxone/ciprofloxacin/levofloxacin PLUS metronidazole

Trunk/extremity (away from axilla/perineum) 1:

• Oxacillin/nafcillin 2 g every 6 hours IV
• Cefazolin 0.5-1 g every 8 hours IV
• Add vancomycin if MRSA risk factors present

Axilla/perineum 1:

• Metronidazole PLUS ciprofloxacin, levofloxacin, or ceftriaxone

Immunocompromised Patients

These patients require aggressive early intervention with broader differential diagnosis 1:

Diagnostic Approach

• Always obtain biopsy or aspiration for histological and microbiological evaluation 1
• Consider bacterial, fungal, viral, and parasitic agents 1
• Risk-stratify by neutropenia severity (high-risk: ANC <100 cells/µL or >7 days duration) 1

Empiric Treatment for Fever and Neutropenia

High-risk patients 1:

• Vancomycin PLUS antipseudomonal coverage (cefepime, carbapenem, or piperacillin-tazobactam) 1
• Target gram-negative bacteria primarily during initial episode 1
• Add MRSA coverage only if skin/soft tissue inflammation present or hemodynamically unstable 1

Duration of Therapy

Most bacterial SSTIs: Continue until clinical resolution, typically 7-14 days 1 Documented infections: Treat based on antimicrobial susceptibilities 1

Critical Pitfalls to Avoid

• Never use systemic antibiotics alone without drainage if abscess is present 2
• Linezolid use in neutropenic patients may delay neutrophil recovery 1
• Monitor doxycycline-treated patients closely at 24-48 hours due to high failure rates 2
• Recognize necrotizing infections early: Look for severe pain disproportionate to findings, rapid progression, bullae, crepitus, or systemic toxicity requiring immediate surgical consultation 1
• In immunocompromised patients, seemingly localized lesions may represent systemic or life-threatening infection 1

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