What is the recommended treatment for a wound culture positive for Methicillin (Oxacillin) Resistant Staphylococcus aureus (MRSA) and Pseudomonas fluorescens/putida?

Treatment for Wound Culture Positive for MRSA and Pseudomonas fluorescens/putida

Based on the wound culture results showing MRSA and Pseudomonas fluorescens/putida, the recommended treatment should include antibiotics that target both pathogens, with selection guided by the susceptibility testing provided in the culture report.

Antibiotic Selection

For MRSA

• The MRSA isolate is susceptible to several antibiotics including vancomycin, linezolid, clindamycin, daptomycin, and trimethoprim-sulfamethoxazole 1
• For outpatient treatment of MRSA wound infections, recommended oral options include:
  • Clindamycin 300-450 mg three times daily (if susceptible) 2
  • Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily 2
  • Linezolid 600 mg twice daily (for more severe infections) 2
  • Doxycycline 100 mg twice daily (note: tetracycline showed intermediate susceptibility in this case) 2

For Pseudomonas fluorescens/putida

• The Pseudomonas isolate is susceptible to meropenem, piperacillin/tazobactam, gentamicin, and tobramycin 1
• It shows resistance to ceftazidime, ciprofloxacin, levofloxacin, and trimethoprim-sulfamethoxazole 1

Treatment Algorithm

1. Assess infection severity:

   • For mild to moderate infections: Oral antibiotic therapy 1
   • For severe infections: Initial parenteral therapy followed by oral therapy when clinically improved 1

2. Recommended regimen based on susceptibilities:

   • For outpatient treatment: Linezolid 600 mg orally twice daily is the preferred option as it is effective against MRSA and can be used as monotherapy 2, 3
   • For inpatient treatment: Vancomycin IV (15-20 mg/kg every 8-12 hours) plus an anti-pseudomonal agent such as piperacillin-tazobactam or meropenem 1, 4

3. Duration of therapy:

   • 5-10 days for uncomplicated infections 2
   • 7-14 days for complicated infections 2
   • Continue until resolution of infection signs and symptoms, but not through complete wound healing 1

Wound Care Considerations

• Appropriate wound care is essential in addition to antibiotic therapy 1
• Debridement of necrotic tissue should be performed if present 1
• Wounds should be kept clean and covered with appropriate dressings 1
• Consider surgical consultation for complex or non-healing wounds 1

Special Considerations

• Avoid rifampin as a single agent or as adjunctive therapy for MRSA skin infections 1
• For recurrent infections, implement preventive measures including:
  • Keep wounds covered with clean, dry bandages 1
  • Maintain good personal hygiene 1
  • Consider environmental hygiene measures for recurrent infections 1

Monitoring Response

• Clinical improvement should be seen within 48-72 hours of appropriate therapy 1
• If no improvement is observed, consider:
  • Reassessing the adequacy of debridement 1
  • Checking for abscess formation requiring drainage 1
  • Evaluating for osteomyelitis, especially if the wound is over a bony prominence 1
  • Adjusting antibiotic therapy based on clinical response and culture results 1

Potential Pitfalls

• Failure to adequately debride necrotic tissue can lead to persistent infection 1
• Inadequate duration of therapy may result in recurrence 2
• Monotherapy with agents that have poor activity against Pseudomonas (such as TMP-SMX alone) may lead to treatment failure 2
• Overlooking the possibility of underlying osteomyelitis, particularly in chronic wounds 1