What is the recommended antibiotic regimen for treating cellulitis?

Recommended Antibiotic Regimen for Cellulitis

For non-purulent cellulitis, empirical therapy should begin with antibiotics active against beta-hemolytic streptococci, such as penicillin, amoxicillin, dicloxacillin, or cephalexin for 5 days, with extension if no improvement is seen. 1, 2

Pathogen Considerations and First-Line Therapy

• Cellulitis is primarily caused by beta-hemolytic streptococci, with Staphylococcus aureus less frequently involved unless associated with penetrating trauma or an underlying abscess 1, 3
• For typical non-purulent cellulitis, first-line therapy should target streptococci with options including:
  • Penicillin
  • Amoxicillin
  • Dicloxacillin
  • Cephalexin 1, 2
• For penicillin-allergic patients, clindamycin or erythromycin are recommended alternatives 1
• The recommended duration is 5 days, with extension if infection has not improved 2, 4

Treatment Algorithm Based on Severity

Mild Cellulitis (Outpatient)

• Oral antibiotics active against streptococci (penicillin, amoxicillin, dicloxacillin, or cephalexin) 1, 5
• For penicillin allergy: clindamycin or erythromycin 1
• Duration: 5 days, extending if no improvement 2, 4

Moderate Cellulitis

• Systemic antibiotics with coverage for streptococci and consideration of adding coverage against methicillin-susceptible S. aureus (MSSA) 1, 6
• Consider hospitalization if concerns for deeper infection or poor adherence to therapy 6

Severe Cellulitis (Hospitalized Patients)

• For complicated skin and skin structure infections requiring hospitalization, empirical therapy for MRSA should be considered pending culture data 2
• Options include:
  • IV vancomycin 2, 1
  • Oral or IV linezolid 600 mg twice daily 2, 7
  • Daptomycin 4 mg/kg/dose IV once daily 2
  • Telavancin 10 mg/kg/dose IV once daily 2
  • Clindamycin 600 mg IV or PO 3 times daily 2
• Duration: 7-14 days, individualized based on clinical response 2

MRSA Considerations

• Empirical coverage for CA-MRSA is not routinely recommended for non-purulent cellulitis 8
• Consider MRSA coverage in patients with:
  • No response to beta-lactam therapy 2
  • Systemic toxicity 2
  • Penetrating trauma 1
  • Evidence of MRSA elsewhere 1
  • Nasal colonization with MRSA 1
  • Injection drug use 1
  • Purulent drainage 1, 9
• In areas with high MRSA prevalence, antibiotics with activity against MRSA (trimethoprim-sulfamethoxazole, clindamycin) may be preferred for empiric therapy 9

Combination Therapy Options

• If coverage for both beta-hemolytic streptococci and CA-MRSA is desired, options include:
  • Clindamycin alone 2
  • TMP-SMX or a tetracycline in combination with a beta-lactam (e.g., amoxicillin) 2
  • Linezolid alone 2, 7

Adjunctive Measures

• Elevate the affected area to promote gravity drainage of edema and inflammatory substances 1, 6
• Treat predisposing conditions such as edema, tinea pedis, or other toe web abnormalities 1, 6
• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adult patients to hasten resolution 1

Prevention of Recurrence

• Identify and treat predisposing conditions such as edema, obesity, venous insufficiency, and toe web abnormalities 1, 6
• For patients with 3-4 episodes per year despite addressing predisposing factors, consider prophylactic antibiotics such as oral penicillin or erythromycin twice daily 1

Common Pitfalls to Avoid

• Failure to examine interdigital toe spaces for fissuring, scaling, or maceration that may harbor pathogens 1, 6
• Not elevating the affected area, which delays improvement 1
• Inadequate treatment duration when clinical improvement is not evident after 5 days 1, 2
• Unnecessary use of broad-spectrum antibiotics for typical non-purulent cellulitis 8