What antibiotic should I prescribe for a patient with a skin infection?

Antibiotic Selection for Skin Infections

For a patient with a skin infection, I recommend starting with clindamycin as first-line therapy for empiric coverage of both streptococci and community-acquired MRSA. 1

Classification and Initial Assessment

The appropriate antibiotic selection depends on the type of skin infection:

• Purulent infections (abscesses, furuncles, carbuncles):

  • Primary treatment is incision and drainage 1
  • Antibiotics generally unnecessary for simple abscesses after drainage unless:
    • Systemic symptoms (fever) present
    • Extensive surrounding cellulitis
    • Immunocompromised host
    • Inadequate source control 1

• Non-purulent infections (cellulitis, erysipelas):

  • Primarily caused by streptococci, sometimes Staphylococcus aureus 1
  • Require antibiotic therapy 1

Empiric Antibiotic Selection Algorithm

For Outpatient Treatment:

1. First-line options (covering both streptococci and CA-MRSA):

   • Clindamycin 300-450 mg orally 3-4 times daily 1

2. Alternative options:

   • TMP-SMX plus a beta-lactam (e.g., amoxicillin) for combined streptococcal and MRSA coverage 1
   • Doxycycline or minocycline (not for children <8 years) 1
   • Linezolid (expensive but highly effective) 1, 2

3. For predominantly streptococcal infections (typical cellulitis/erysipelas without purulence):

   • Cephalexin 500 mg orally 4 times daily 3, 4
   • Dicloxacillin for MSSA infections 2, 5

For Hospitalized Patients with Complicated Infections:

• Vancomycin IV (first-line for hospitalized patients) 1
• Daptomycin 4 mg/kg IV daily 1
• Linezolid 600 mg IV/PO twice daily 1
• Ceftaroline IV 1

Special Considerations

• Duration of therapy: 5-10 days for uncomplicated infections, individualized based on clinical response 1

• Pediatric patients:

  • Mupirocin 2% topical ointment for minor skin infections 1
  • Avoid tetracyclines in children <8 years 1
  • For hospitalized children, vancomycin or clindamycin are recommended 1

• Risk factors for MRSA (requiring empiric MRSA coverage):

  • Prior MRSA infection or colonization
  • Recent hospitalization
  • Recent antibiotic use
  • Injection drug use
  • Presence of abscess
  • Systemic inflammatory response 1

Common Pitfalls to Avoid

• Avoid rifampin as a single agent or as adjunctive therapy for skin infections 1
• Avoid unnecessary broad-spectrum coverage against gram-negative bacteria unless treating complex abscesses or in immunocompromised patients 1, 6
• Don't neglect source control - incision and drainage is the primary treatment for abscesses, with antibiotics being adjunctive 1
• Don't overlook the need for cultures in patients with:
  • Treatment failure
  • Severe or complicated infections
  • Immunocompromised status
  • Suspected outbreak 1

Prevention of Recurrent Infections

For patients with recurrent skin infections:

• Maintain good personal hygiene with regular bathing 1
• Keep draining wounds covered with clean, dry bandages 1
• Consider decolonization with intranasal mupirocin and chlorhexidine washes for recurrent S. aureus infections 1