What antibiotics are recommended for the treatment of cellulitis?

Antibiotic Treatment for Cellulitis

For nonpurulent cellulitis, first-line treatment should be a 5-day course of antibiotics active against beta-hemolytic streptococci, such as penicillin or a first-generation cephalosporin like cephalexin. 1

Classification and Initial Antibiotic Selection

Nonpurulent Cellulitis (No Purulent Drainage or Abscess)

• First-line therapy: Target beta-hemolytic streptococci 1

  • Penicillin VK 250-500 mg every 6 hours orally
  • Cephalexin 500 mg four times daily orally
  • Clindamycin 300-450 mg three times daily orally (for penicillin-allergic patients)

• Duration: 5-6 days is sufficient for most cases 1

  • Extend treatment only if infection has not improved within this period

Purulent Cellulitis (With Purulent Drainage/No Abscess)

• First-line therapy: Target both streptococci and CA-MRSA 1

  • Clindamycin 300-450 mg three times daily orally
  • Trimethoprim-sulfamethoxazole (TMP-SMX) plus a beta-lactam (e.g., amoxicillin)
  • Doxycycline or minocycline plus a beta-lactam
  • Linezolid 600 mg twice daily orally (more expensive option)

• Duration: 5-10 days, individualized based on clinical response 1

Special Considerations

Risk Factors for MRSA

Consider empiric MRSA coverage if the patient has:

• Previous MRSA infection or colonization
• Penetrating trauma
• Injection drug use
• Systemic inflammatory response syndrome (SIRS)
• Athletes, prisoners, military recruits, or residents of long-term care facilities 2
• No response to initial beta-lactam therapy 1

Hospitalized Patients with Complicated SSTI

• First-line options: 1

  • Vancomycin IV
  • Linezolid 600 mg IV/PO twice daily
  • Daptomycin 4 mg/kg IV once daily
  • Telavancin 10 mg/kg IV once daily
  • Clindamycin 600 mg IV/PO three times daily

• Duration: 7-14 days based on clinical response 1

Approach to Treatment Failure

1. If no improvement after 48-72 hours on beta-lactam therapy:

   • Consider adding or switching to MRSA-active agent 1
   • Obtain cultures if possible
   • Consider deeper infection or alternative diagnosis

2. If worsening despite appropriate therapy:

   • Consider hospitalization
   • Evaluate for abscess formation (ultrasound may help)
   • Consider broader coverage or IV antibiotics

Prevention of Recurrence

• Treat predisposing factors:

  • Tinea pedis or interdigital maceration 1
  • Edema (compression, elevation)
  • Skin barrier issues (emollients for dry skin)

• For frequent recurrences (3-4 episodes per year):

  • Consider prophylactic antibiotics:
    • Monthly benzathine penicillin 1.2 MU IM
    • Oral penicillin V 1 g twice daily
    • Oral erythromycin 250 mg twice daily 1

Common Pitfalls

1. Overtreatment pitfalls:

   • Using unnecessarily broad-spectrum antibiotics
   • Prescribing combination therapy when single agents are sufficient
   • Treating for longer than necessary (>5-6 days for uncomplicated cases) 1, 3

2. Undertreatment pitfalls:

   • Failing to recognize risk factors for MRSA
   • Not adjusting therapy when patients fail to respond
   • Not addressing underlying predisposing conditions

3. Diagnostic pitfalls:

   • Confusing cellulitis with other inflammatory conditions
   • Missing an underlying abscess that requires drainage
   • Not obtaining cultures in severe or non-responsive cases 1

Remember that while cultures are not routinely needed for typical cellulitis, they should be obtained in cases of treatment failure, severe infection, or immunocompromised patients 1.