What is the most appropriate oral antibiotic regimen for a patient with a purulent skin abscess due to methicillin-susceptible Staphylococcus aureus (MSSA) at the time of discharge?

Oral Antibiotic Regimen for MSSA Skin Abscess at Discharge

Clindamycin 600 mg orally every 8 hours is the most appropriate oral antibiotic regimen for JJ at discharge for treatment of MSSA skin abscess. 1, 2

Rationale for Selection

Assessment of Patient Factors

• 53-year-old female with purulent skin abscess (surgically drained)
• Initial blood culture positive for MSSA
• Repeat cultures negative within 48 hours of IV antibiotics
• Day 9 of antibiotic therapy
• Clinically stable for discharge

Antibiotic Selection Process

1. Clindamycin (600 mg every 8 hours)

   • Recommended by IDSA guidelines for skin and soft tissue infections 1
   • Effective against both MSSA and streptococci
   • Appropriate dosing for adults is 300-450 mg four times daily or 600 mg three times daily 2
   • Good tissue penetration for skin/soft tissue infections

2. Trimethoprim-sulfamethoxazole (400 mg/80 mg every 12 hours)

   • While effective against MSSA, the IDSA guidelines note it has "limited published efficacy data" 1
   • More commonly used for MRSA infections rather than MSSA 2
   • The proposed dose (400/80 mg twice daily) is lower than recommended (1-2 double-strength tablets twice daily) 2

3. Vancomycin (125 mg every 6 hours)

   • Oral vancomycin has poor systemic absorption
   • Primarily used for C. difficile infections, not for systemic MSSA infections
   • Not recommended for skin/soft tissue infections requiring systemic therapy 1

4. Linezolid (600 mg every 12 hours)

   • Reserved for severe cases or treatment failures 2
   • Unnecessarily broad-spectrum for known MSSA infection
   • More expensive with greater potential for adverse effects
   • Should be preserved for resistant organisms 3

Treatment Duration and Monitoring

• The IDSA recommends 5-10 days of therapy for skin and soft tissue infections 1, 2
• Since JJ has already received 9 days of IV therapy, a 5-7 day course of oral clindamycin would be appropriate to complete treatment
• Monitor for potential adverse effects of clindamycin including:
  • Gastrointestinal symptoms (diarrhea)
  • C. difficile-associated diarrhea
  • Rash

Common Pitfalls to Avoid

1. Inadequate spectrum of activity: Ensure the selected antibiotic covers the identified pathogen (MSSA)

2. Inappropriate dosing: The correct dose for clindamycin is 600 mg every 8 hours for adequate tissue levels 4

3. Unnecessary broad-spectrum coverage: Avoid linezolid which should be reserved for resistant organisms or treatment failures 3, 5

4. Failure to consider local resistance patterns: Be aware of potential inducible clindamycin resistance, though this is more common with MRSA than MSSA 5

5. Neglecting source control: Ensure adequate surgical drainage has been performed (which was done in this case)

By following these recommendations, JJ should receive appropriate oral antibiotic therapy to complete treatment of her MSSA skin abscess following hospital discharge.