Is cefazolin (Ancef) IV effective for treating a post-surgical wound infection with a swab positive for Staphylococcus (Staph), Streptococcus (Strep), and Enterococcus faecalis (E. faecalis)?

Treatment of Post-Surgical Wound Infection with Staph, Strep, and E. faecalis

Cefazolin IV is not adequate as monotherapy for a post-surgical wound infection with Staphylococcus, Streptococcus, and Enterococcus faecalis because E. faecalis is intrinsically resistant to cefazolin.

Microbiology and Coverage Considerations

• Cefazolin is effective against:

  • Staphylococcus aureus (including beta-lactamase-producing strains) 1
  • Streptococcus species 1

• However, cefazolin lacks coverage for:

  • Enterococcus faecalis (intrinsically resistant to cephalosporins) 1

Appropriate Treatment Approach

First-Line Treatment

1. Surgical Management:

   • Incision and drainage is the cornerstone of treatment for infected surgical wounds 2
   • Obtain cultures during drainage to confirm susceptibility patterns 2

2. Antibiotic Therapy:

   • For coverage of all three organisms (Staph, Strep, and E. faecalis), use:
     • Ampicillin-sulbactam (Unasyn) 3g IV q6h OR
     • Piperacillin-tazobactam (Zosyn) 4.5g IV q6-8h

Alternative Regimens

• For patients with penicillin allergy:

  • Vancomycin 15-20mg/kg IV q8-12h (for Staph and Strep) PLUS
  • Gentamicin 5mg/kg/day IV (for E. faecalis) 2

• For less severe infections with confirmed susceptibilities:

  • Amoxicillin-clavulanate 875/125mg PO BID (provides coverage for all three organisms)

Treatment Duration and Monitoring

• Duration:

  • Mild infections: 5-7 days 3
  • Moderate-severe infections: 10-14 days 3

• Reassessment:

  • Evaluate clinical response after 48-72 hours 3
  • If no improvement, consider:
    • Inadequate drainage
    • Resistant organisms
    • Deep tissue involvement requiring imaging

Why Cefazolin Alone Is Inadequate

1. Enterococcus faecalis Resistance:

   • E. faecalis is intrinsically resistant to all cephalosporins including cefazolin 1
   • This resistance is chromosomally mediated and universal

2. Evidence-Based Approach:

   • Guidelines recommend antibiotics that cover all identified pathogens in post-surgical infections 2
   • When multiple organisms are present, therapy must address all pathogens

Special Considerations

• Biofilm Formation:

  • Surgical wounds with foreign material may have biofilm formation
  • More aggressive debridement and longer antibiotic courses may be needed

• Antibiotic Stewardship:

  • While cefazolin is excellent for surgical prophylaxis 2, treatment of established polymicrobial infections requires broader coverage
  • Once susceptibilities are known, therapy can be narrowed if appropriate

• Pitfall to Avoid:

  • Treating only the most common pathogen (Staph) while ignoring E. faecalis could lead to treatment failure and persistent infection

Remember that proper surgical drainage combined with appropriate antibiotic therapy targeting all identified pathogens is essential for successful treatment of post-surgical wound infections.