What is the next step in treating a post-surgical patient with a skin infection that is unresponsive to amoxicillin (amoxicillin)?

Treatment for Post-Surgical Skin Infection Unresponsive to Amoxicillin

For a post-surgical patient with skin infection unresponsive to amoxicillin, the next step should be switching to a broader-spectrum antibiotic regimen such as vancomycin plus piperacillin-tazobactam, or ceftriaxone plus metronidazole, with or without vancomycin based on MRSA risk factors. 1

Rationale for Treatment Change

• Post-surgical skin infections unresponsive to amoxicillin likely involve resistant organisms, particularly methicillin-resistant Staphylococcus aureus (MRSA), which has emerged as the leading cause of postoperative infections 1
• Nosocomial postoperative infections require coverage against a broader spectrum of pathogens including Pseudomonas aeruginosa, Enterobacter species, Proteus species, MRSA, enterococci, and potentially anaerobes 1
• Treatment failure with amoxicillin suggests either resistant organisms or a polymicrobial infection requiring broader coverage 1

Recommended Treatment Options

First-line options:

• For incisional surgical site infections after intestinal/genitourinary surgery:

  • Piperacillin-tazobactam 1
  • Ceftriaxone plus metronidazole (with or without vancomycin) 1
  • Carbapenem (imipenem, meropenem, or ertapenem) 1

• For incisional surgical site infections after surgery of trunk or extremity:

  • Vancomycin (if MRSA is suspected) 1
  • Clindamycin (if MRSA is suspected but no systemic toxicity) 1
  • Linezolid (alternative for MRSA coverage) 1

For severe infections:

• Vancomycin plus piperacillin-tazobactam 1
• Linezolid 600 mg IV/PO twice daily 1
• Daptomycin 4 mg/kg IV once daily 1

Treatment Algorithm

1. Assess infection severity and location:

   • Determine if the infection involves a surgical site near intestinal/genitourinary tract or trunk/extremity 1
   • Evaluate for systemic symptoms (fever, tachycardia, hypotension) 1

2. Obtain cultures before changing antibiotics:

   • Wound cultures and blood cultures if systemically ill 1
   • Gram stain of infected material (presence of Gram-positive bacilli should not be discounted) 2

3. Consider source control:

   • Surgical debridement or drainage if abscess is present 1
   • Remove infected hardware or bone flaps if present 2

4. Select appropriate antibiotic regimen based on location:

   • For intestinal/genitourinary surgical site: piperacillin-tazobactam or ceftriaxone plus metronidazole 1
   • For trunk/extremity away from axilla/perineum: vancomycin or linezolid if MRSA suspected 1
   • For axilla/perineum: ceftriaxone or fluoroquinolone plus metronidazole 1

5. Duration of therapy:

   • 7-14 days for complicated skin and soft tissue infections 1
   • Duration should be based on clinical response and source control success 1

Important Considerations

• MRSA coverage is essential in post-surgical patients not responding to initial therapy, as MRSA is associated with a three-fold greater 90-day mortality rate compared to methicillin-susceptible S. aureus infections 1
• Local resistance patterns should guide empiric therapy choices 1
• Patient-specific factors such as drug allergies, renal function, and prior antibiotic exposure must be considered 1
• Avoid unnecessarily prolonged therapy as treatment beyond 7 days for uncomplicated infections provides little additional benefit 3

Common Pitfalls to Avoid

• Continuing ineffective therapy: Failure to switch antibiotics promptly when initial therapy is ineffective increases morbidity and mortality 1
• Inadequate source control: Antibiotics alone may be insufficient without proper drainage or debridement 1
• Overlooking polymicrobial nature of post-surgical infections, which often require coverage for both gram-positive and gram-negative organisms 1
• Underestimating the role of MRSA in post-surgical infections, which has become increasingly prevalent in healthcare settings 1