What is the best antibiotic choice for Methicillin-Sensitive Staphylococcus Aureus (MSSA) epidural abscess?

Nafcillin is the First-Line Antibiotic Choice for MSSA Epidural Abscess

For methicillin-sensitive Staphylococcus aureus (MSSA) epidural abscess, nafcillin (or equivalent antistaphylococcal penicillin) is the first-line antibiotic treatment of choice. 1

Treatment Algorithm for MSSA Epidural Abscess

First-Line Treatment:

• Nafcillin: 1-2 g IV every 4 hours 1, 2
  • Duration: At least 6 weeks for complicated infections involving abscess formation 1

Alternative Options (for penicillin allergies):

1. Non-anaphylactoid reactions (e.g., simple skin rash):

   • Cefazolin: 1 g IV every 8 hours 1, 3, 4

2. Anaphylactoid reactions (severe penicillin allergy):

   • Vancomycin: 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) 1, 5
   • Daptomycin: ≥8 mg/kg IV daily (for left-sided infections) 1

Evidence Supporting Nafcillin as First Choice

The American Heart Association (AHA) guidelines specifically recommend nafcillin for brain abscess resulting from MSSA infections, stating that "nafcillin should be used instead of cefazolin" due to superior blood-brain barrier penetration 1. This recommendation is particularly relevant for epidural abscesses, which involve the central nervous system.

The FDA label for nafcillin specifically indicates it for "treatment of infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drug" 2, which includes MSSA infections.

Comparative Effectiveness

While recent research suggests cefazolin may be similarly effective to antistaphylococcal penicillins for MSSA epidural abscess treatment 3, 4, the AHA guidelines still favor nafcillin specifically for CNS infections. A 2021 study found no significant differences in treatment failure, mortality, or recurrence rates between cefazolin and antistaphylococcal penicillins for MSSA spinal epidural abscess 3.

Important Clinical Considerations

• Surgical drainage is essential alongside antibiotic therapy for epidural abscesses 5
• Duration of therapy should be at least 6 weeks for complicated infections involving abscess formation 1
• Avoid gentamicin as it is not recommended for treatment of staphylococcal infections in this context 1
• Blood-brain barrier penetration is a key factor in antibiotic selection for CNS infections, giving nafcillin an advantage over cefazolin 1

Common Pitfalls to Avoid

1. Using cefazolin for CNS infections: Despite similar efficacy in some studies, cefazolin has inadequate blood-brain barrier penetration compared to nafcillin 1

2. Inadequate treatment duration: Epidural abscesses require prolonged therapy (at least 6 weeks) due to their complicated nature 1

3. Delayed surgical intervention: Antibiotics alone are often insufficient; prompt surgical drainage is typically necessary 5

4. Failure to adjust therapy based on culture results: Always confirm susceptibility and adjust therapy accordingly 2

5. Using clindamycin as monotherapy: Clindamycin has been associated with IE relapse and is not recommended for serious staphylococcal infections 1

In summary, while several antibiotics show activity against MSSA, nafcillin remains the preferred agent for MSSA epidural abscess due to its excellent CNS penetration, established efficacy, and strong recommendation in guidelines specifically addressing CNS infections caused by MSSA.