What is the treatment for a prosthetic knee infection caused by Staphylococcus (Staph)?

Treatment of Prosthetic Knee Infections Caused by Staphylococcus

The treatment of prosthetic knee infections caused by Staphylococcus requires a combined surgical and antimicrobial approach, with debridement and retention (DAIR) for early infections and prosthesis exchange for chronic infections, along with 3-6 months of biofilm-active antibiotics including rifampin combinations for susceptible strains. 1, 2

Surgical Management Options

The surgical approach depends on several key factors:

Early Infections (symptoms <4 weeks, implant age <6-13 weeks)

• DAIR (Debridement, Antibiotics, Irrigation, and Retention) is recommended when:
  • Duration of symptoms is less than 4 weeks
  • Implant age is less than 6-13 weeks
  • Prosthesis is stable
  • Biofilm-active antibiotics are available
  • Good quality soft tissue is present 1

Chronic Infections or Failed DAIR

• Exchange Procedure (one-stage or two-stage):
  • One-stage exchange: Complete removal and immediate reimplantation
  • Two-stage exchange: Removal, placement of antibiotic-loaded spacer, and delayed reimplantation (after 6+ weeks) 1, 2

Salvage Procedures (for recalcitrant infections)

• Implant Resection (without reimplantation)
• Arthrodesis (joint fusion)
• Amputation (in extreme cases with severe bone loss or uncontrolled infection) 1

Antimicrobial Therapy

For Methicillin-Susceptible Staphylococcus aureus (MSSA)

1. Initial therapy (2-6 weeks):

   • Nafcillin 1.5-2g IV q4-6h OR
   • Cefazolin 1-2g IV q8h OR
   • Ceftriaxone 1-2g IV q24h 1, 2, 3

2. Followed by oral therapy with rifampin combinations:

   • Rifampin 300-450mg PO twice daily PLUS
   • Ciprofloxacin 750mg PO twice daily (preferred companion drug) OR
   • Levofloxacin 750mg PO daily OR
   • Alternative companions: co-trimoxazole, minocycline, doxycycline, or oral first-generation cephalosporins 1, 2

For Methicillin-Resistant Staphylococcus aureus (MRSA)

1. Initial therapy (2-6 weeks):

   • Vancomycin 15mg/kg IV q12h OR
   • Daptomycin 6mg/kg IV q24h 1, 2, 4

2. Followed by oral therapy with rifampin combinations (as above, using appropriate companion drugs based on susceptibility) 1, 2

Duration of Antimicrobial Therapy

The duration depends on the surgical approach:

• DAIR procedure:

  • 3 months for hip infections
  • 6 months for knee infections 1, 2

• One-stage exchange or early reimplantation:

  • 3 months of antimicrobial therapy with biofilm activity 1, 2

• Two-stage exchange with delayed reimplantation:

  • 6 weeks of antimicrobial therapy 1, 2

• Resection arthroplasty or amputation:

  • 6 weeks of antimicrobial therapy, or 24-48 hours after procedure if all infected tissue removed 1

Risk Factors for Treatment Failure

Several factors are associated with poor outcomes and should guide treatment decisions:

• History of rheumatoid arthritis 5
• Late infection (>2 years after arthroplasty) 5
• Elevated ESR (>60 mm/h) at presentation 5
• Symptom duration >1 week before intervention 6, 5
• Staphylococcus aureus infection (particularly MRSA) 1, 6
• Presence of sinus tract 1
• Hematogenous infections (58% success vs. 93% for acute postoperative) 6

Important Considerations and Pitfalls

1. Never use rifampin as monotherapy - always combine with another active agent to prevent resistance development 1, 2

2. Monitor for drug interactions with rifampin - particularly with:

   • Warfarin and other anticoagulants
   • Immunosuppressants
   • Glucocorticoids
   • Other antimicrobials 1, 2

3. Watch for fluoroquinolone adverse effects - including:

   • Tendinopathy
   • Risk of aortic ruptures
   • Central nervous system effects 1

4. Regular monitoring is essential:

   • Liver function tests for patients on rifampin
   • Inflammatory markers (1-3 monthly)
   • Follow up for at least 12 months after cessation of antimicrobials 1, 2

5. Consider alternative surgical approaches for difficult-to-treat organisms like MRSA 1

By following this algorithmic approach based on infection timing, organism identification, and patient factors, prosthetic knee infections caused by Staphylococcus can be effectively managed to optimize outcomes related to morbidity, mortality, and quality of life.